GPS-Receivers

Five steps for choosing the best car of GPS navigation written by: Joyce Li

2011-09-20T05:38:00.000-05:00

Views: View (s 559) as far as we know, there are many car GPS navigation units, and they are complex, so it is impossible for an unprofessional person to choose the right for your car. Then I am happy to experience how one the best car GPS navigation for in this chapter to automatically select.

So, I will show that you ask the way to configure, see build in the GPS navigation system for your car in the first part of the below information.

First of all, see you, how much you based in dash GPS system for your car, want to spend on your personal financial situation. This will help you narrow your selection, GPS systems, and a spending limit. It will help to avoid expenditure consumers when buying a GPS navigation system.

Secondly, list portable GPS navigation system functions, that you, as the United States in details, voice guidance, a small color screen, touchscreen, Assembly suction, search Bluetooth capabilities for use as a mobile phone handsfree accessories and power supply. This kind of in shock GPS navigation system is suitable for occasional use. They are very easy and will be able to help you while driving.

Thirdly, visit so many online retailers or visit a few shops nearby, as you like, to look at the available GPS navigation systems. When shopping for GPS navigation, search devices, for units that meet the criteria laid down. Write functions, GPS brand, price and GPS model name/number of each navigation unit that created the criteria fulfilled for the purchase of your new GPS navigation system.

Fourthly, a major disadvantage of the in-dash-GPS navigation system is the lack of an internal compass, accelerometer or a device used to measure the speed. Without this feature, it is not as accurate as a build-in GPS-system when the navigated there is no GPS signal. If you live in an area where there many tunnels, skyscrapers or the GPS is used very often, it is important to buy a more complex portable GPS system, which has a build-in accelerometer.

Finally, decide which GPS system you buy, are based on price, features, and your hobby. Then you buy the system unit of GPS navigation on the store or online retailer.

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Mobile phones and GPS posted by: Sanjeev Walia

2011-09-20T01:38:00.000-05:00

Number of views: 114 view (s) GPS is a global navigation satellite system, which determines that the exact geographical location of the GPS enabled device by calculating the time difference for signals from different satellites the receiver.

This technology was originally developed by the American Department of Defense, for military purposes only, but today it worldwide used navigation aid which most frequently and is a profound impact on trade and civilian life.

GPS is to change our lives; It has brought us a new range of information, a new revolution in the wireless age. The technology is spreading, but a lot of people are still nothing of his virtues and capacity. We can to keep everything and everyone in transit, he can tell you exactly where you are, if you get lost, and it can run through the streets of every associated city and can even say, links, those that you never noticed before. It is soon to make worthy city maps artifacts in the archaic Museum Street.

The mobile phone is today the most used and popular GPS-enabled device. Is it not very surprising? The phone has developed over the years, to a variety of tools and features, to once unimaginable, so many devices out of date to integrate. The non-exhaustive list includes text-messaging, E-mail, Internet, music player, camera, and Bluetooth, to name a few. Most mobile phones virtually converter, calculator, calendar, timer, stopwatch and alarm today with built-in but essential applications such as unit.

GPS only added to the comprehensive utility of the phone. A cell enhanced capacity in two ways. As a GPS enabled device, it allows you to track the exact location of the phone, so you help to keep track of your love. Also makes it easier, look for the phone as lost or stolen. The other way in which it exceeds your expectations, is acting as a really trusted Navigator; Your phone whether you go the unexplored part of your city or even halfway around the world, would never, you will not show you the right way.

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Notes to safety when driving with DVD GPS navigation system written by: Joyce Li

2011-09-19T21:38:00.000-05:00

Number of views: the 111 view as technology development (s), install more and more people dvd GPS navigation system in the car, so that the entertainment of the driver will attract attention, while the vehicle is in motion. Make sure the driver Safery, please use the device not while driving on the move. All safety instructions are to read and understand before you store this product in operation and please you this guide in the vehicle for your future reference. Now you see the tips below.

One tip, make sure that the product safely operated, that will jeopardize any other road users.

Tip two, this is an electronic device, please use the device in dangerous conditions, such as in gas stations, chemical, or electromagnetic radiation areas.

Tip three, satellite navigation system, which is installed for the directional reference in this device and is used only of advice. It represents not the traffic rules and takes not the flow of traffic in considerations if the routes are selected.

Tip four, please try not to install, uninstall or repair the device with their power turned on, as it is dangerous, and also the unit can be damaged. Turning professional for installation, remove or repair services if necessary.

Tip five, please not this uit on dangerous substances.

Tip five for LCD touch screen monitor, please not scratching or Preatch or press the screen with any hard or sharp object, the may be directly or press the screen with a hard or sharp object, directly or indirectly could damage the LCD screen.

Tip five, please, add any standard 12 cm CD/VCD/DVD disc into the drive on the device equipped, otherwise it can damage the disc scan system.

Tip five when the temperature in the car under direct sunlight is too high that turn please possible to prevent unit overheating the air conditioner before turning on the unit.

Tip six, please use the clean disk, or it can cause, that the noise of the DVD.

Seven, please regularly clean tip DVD laser with disk cleaner.

Please carefully drive and enjoy your dvd GPS navigation travel.

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GPS antennas written by: Joe Golz

2011-09-19T17:38:00.000-05:00

Number of views: A-GPS is only as good as the GPS signals, which could get it, so why not ensure that you receive the very best signals 114 view (s)

GPS antennas are priceless electronic gearing, but field conditions are sometimes hard and can affect them adversely. GPS antennas are getting better and better, and you definitely get indoors, the GPS signal, but it is not always safe.

GPS antennas are devices that supports expanding the reception signal to a GPS receiver, whether it's a standalone receiver or a receiver embedded. A GPS antenna in a situation is often used, where the GPS receiver itself somehow far away from a line of sight to the sky (such as in a vehicle), the support of the GPS receiver is in the air without for be moved. GPS antenna can be purchased for a distribution of households. Versions is quite common with cheaper home.

Reception of GPS signals may be only then trustworthy, if the antenna has an open vision of heaven. Passive GPS antennas contain a low noise amplifier (LNA). When connected to a GPS, it is the internal amplifier into the GPS, which strengthened the weak signal of the passive antenna.

So if a passive antenna use? In conditions you would have the open air a clear overview of but if something, look at the sky, which means that it is installed, has your GPS receiver, in the automotive or somewhere hidden.

Of different kinds of indoor GPS antennas can be found.
Inner GPS antennas:

If GPS antennas with a GPS connected, it is the internal amplifier within the GPS receiver which amplifies the weak signal of the passive antenna.
Internal GPS antennas means that they are created within the GPS receiver itself. External antennas are an option for some models. All GPS have built over an internal antenna. The performance of the recipient is dimension in relation to the antenna (the bigger, the better).

The internal patch antenna, the conductor is a square on square piece of metal is positioned. The advantage of the patch antenna is that it again went the satellite signal faster if they lost. Maintain the face of GPS units for best efficiency with internal patch antenna to and parallel to the Earth.

The second type is internal Quad Helix a pole with wire is wrapped. They are particularly sensitive to GPS signals. Maintain for best efficiency the GPS in the order, that the antenna to the sky shows.

External GPS antennas:
Extern means that it is not built, in or on the GPS receiver. External GPS antennas are useful if the GPS in a place, where the view of the sky like a car, boat or an airplane is blocked.

Reradiating GPS antennas:
I f the GPS receiver has not connected socket for external antenna should you use a reradiating GPS antenna, including two antennas: receiving the signal from the satellite, and the other is connected to the first and is located close to the GPS receiver. The effects are connected to the GPS receiver as an external antenna.

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FAQ for use of the rear-view mirrors GPS navigation written by: Joyce Li

2011-09-19T13:38:00.000-05:00

Number of views: 229 1. GPS problems view (s)

If you can receive not the signal, please be sure to some of the reasons as follows:
A.Please make sure, that is no refuge in the sky
B.das weather is bad
C.too many shelters (high building, the vehicle explosion-ban diaphragms, tunnels, viaducts, trees ect.)
D.There are other wireless transmission of Enquipments.
E. car-ex-protection membranes and the screen with high temperatures

2. What can I do as the card is lost during formatting?

Show data backup is available in the CD.You should unzip the data of folder "GPS map" of the CD-ROM in the SD card.After you insert the card into the GPS Navigator turn required in the system, activation code, and enter the correct (name) according to your dealer for the references to reactive the navigation system.

3. Why the standby time is of instruments of navigation sometimes too short?

A. the duration of the lithium battery depends on the ambient temperature changes and the service Bedingungen.Wenn which is too low or too high ambient temperature, will be affected for the duration of the battery.It is recommended to use this device at room temperature.

B. If the device is used, larger screen of the navigation device requires more power. Moreover, the actual duration can be from the volume boost sound field of special effects and other factors such as frequent operation specified differently affected, to some extent.If the car is used, is recommended, close the car charger, and download the device while using it.

4. How long would the positioning after completed - turn?

the Navigator should the requirements of the first positional parameter with the 60's in the same place under clear Himmel.Aber the time, the position is sometimes affected by factors such as satellite signal-Scheller.SA disrupt (block - mountain or building) climate, environment, etc.

5. Why do the positioning take longer at some point?

The time to the position may be longer in the following situations:
A. GPS satellites throughout the local zone not equal

As GPS signal can not penetrate the opaque solid questions, and receive the signal tree, of the vehicle explosion-ban on expert opinion is accommodation such as buildings, tunnels, Bock, membrane, etc, as well as weather conditions such as covered and rainy day.

C. receive GPS signal would be also affected and of thick-film or tear film that contains some mental element.

6. Is it free, reception of GPS satellite signal with the Navigator?

Yes, the GPS signal reception is free of charge.

7. Why is that some film that files can be played while others of the same format can not be played?

Incompatibility can occur because there are different compilation modes and solutions for the files of the same format on current websites.All you have to do is, convert their format with recommended conversation tool on the disk are attached before they play.

8. How about the accuracy of the Navigator?

The accuracy of GPS, army, comes from the Statellite position technology of the United States is complete the influence for the accuracy of the GPS satellite signal of the United States.The official according to the accuracy is within 10 m; and frequently, it can be in 6 meters in more than 90% accurate time.

9. As for abnormal shutdown of the Navigator to do?

First, press the POWER button on the control panel of the device and see whether the restart normally or not.
Then check your power supply cable backup, change, if it is defective.

If you meet problem, that you can not find the answer in the FAQ, or you can not cope when with the rear-view mirrors, please ask us for help from the contract.

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GPS tracking device: Protect your car against theft written by: John Morgan

2011-09-19T09:38:00.000-05:00

Number of views: 501 view (s) the thought of losing the prices car - car, van, truck etc - is what is goose, the owner of the car bumps. We strive to protect our vehicle, but thieves sometimes are smarter than us and succeeds to steal in under our nose. Although it measures to reduce the Palace door theft, such as insurance, but it is not the best of the options. Should be like the focus only on the vehicle to protect from theft. GPS tracking device is the solution. The device is efficiently used to keep track of the whereabouts of the vehicle, and sends also alerts in the instance of a breach of the preset virtual geo fences or speed limits.

GPS tracking device to become a household name in these days because of its impeccable features and security solutions. The device works on GPS technology. The technology, the satellite orbiting around the Earth is used to find the whereabouts of any object placed on Earth.

GPS tracking device not only offers security solutions for the users, but also by the users who like to like to track track location of its fleet of vehicles and users, on their child teenager fleet managers, that the visits and stops of their spouse etc popular scout.

The GPS tracking device is a small, portable device that is easy to install at any time. The best feature of the device is that once installed, it works with the ODB (on-board diagnosis) of the vehicle and works even if the vehicle's engine is turned off. Most of GPS tracking devices Web are based, the tracking in real time of the vehicle in the form of graphical presentation (e.g., cards) to facilitate customized Web portals on Internet. This custom-tailored Web portals are created for each user and the purchase of GPS tracking device are given them at the time whose access IDs to look impeccable persecution of her vehicle.

The GPS-tracking device offers function set virtual geo fences for the vehicle, in violation of this geo fence (i.e. on every move by car), the device sends signals in the form of E-mails or SMS messages warning to the user. So investor warnings and protects the vehicle against theft.

If anything, the vehicle is stolen, the GPS tracking device reflects information about the location of the vehicle on the custom Web portal on the Internet. Therefore it makes it easier for the user of the stolen car in absolutely no time to recover. The GPS tracking device is certainly a perfect device that unique vehicle provides security for the special user.

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To solve, such as the common problems when run GPS navigation devices from provided: Joyce Li

2011-09-19T05:38:00.000-05:00

GPS articles
How to solve common problems when run GPS navigation unit of expert author: Joyce Li word count: 689 words

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Ambulance services and GPS posted by: Sanjeev Walia

2011-09-19T01:38:00.000-05:00

Number of views: the time required for the response to a request to 102 request 175 view (s) for urgent medical assistance and emergency medical services, can make the difference between life and death. • to get to the point of despair as quickly as possible, which must be ambulance crew know exactly where they are needed and the fastest way and way / route there. • must they, the shortest and the least congested route and the nearest hospital, who know the location of the patient's needs.

A technique in our increasingly wired world of the 21st century, which allows us to these challenges is GPS. A GPS-enabled device built into an ambulance can on the ambulance driver and crew not only directed by the place where the stress call been made, but would identify also the shortest route to their destination.

The next medical facilities available for the patient to recognize a costumed GPS device with the correct uploaded data. In addition, it can advice the ambulance crew with the detailed functions of various hospitals and clinics, allowing them to choose medical facility, from the appropriate services for the patient.

Ways in which GPS advantageous for emergency services can be, is fleet management. A full-featured GPS system can provide a minute by minute update the location of each ambulance back to the base or the control center. This enables better monitoring of the fleet, and makes it possible to keep every ambulance in the area a close watch on. With the help of GPS, which the caller informed the Centre with the progress of the ambulance to can help most people stress situation find scary in when ever an emergency call is made.

Slowly but steadily the number of GPS enabled ambulance in India grows. It is regrettable that enormous costs for the full adoption of GPS by ambulance acts to slow down the overall application of GPS in this area of services. Are still on local level steps is taking to integrate GPS technology in our ambulance fleets.

The Red Cross Health Department in Panchkula district updated it with 18 fleet GPS ambulance activated in November 2009. The same happened in Nagpur with 30 ambulances in May 2009 by the NMC. • the Bihar Government initiated in June 2009 to just a few examples to give a pilot project with 10 ambulances. Although progress is being made, yet not the majority of our ambulances GPS on board, especially in small towns and rural India.

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How do you choose the GPS-maps for your car? Created by: Joyce Li

2011-09-18T21:38:00.000-05:00

Number of views: 303 view (s) is present, there are many kinds of GPS maps. In this part we are comparing the most good quality GPS cards, they are associated with IGO maps, Garmin maps, maps of TomTom and Route66.

IGO map

IGO is really fast for navigation, especially if you live in Europe thinks most users iGO is the best. Now I'm like some features for iGO8 list, then we could examine and select the best a.

New features

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What makes good GPS by written: Sanjeev Walia

2011-09-18T17:38:00.000-05:00

View (s views: 159) now that you are, you make something, want to buy a GPS device, is put into a serious question in your mind. Pray, what makes a good GPS? How would the qualities and abilities of various GPS systems on the market? Cheaper are systems better? Should I search more features? All these questions are required in your head explode.

Basically, the choice has the same basis as the selection of electronic devices or car a GPS. First, you need to know what you need, what you are looking for. Do you need it, to help you if you are hiking? Or do you need to help you weave it through traffic. Or, you have to it for both! Down below, are a few wide aspects that you need to be careful.

Screen size is an important feature for GPS devices. A larger screen offers a larger map view and more context, where you are and what will come. But then again, the screen may be described not as big as bulky. I mean Hey, you want to a theatre on the dashboard, you wear? Ideally, something best is about 3.5 to 4.7 inches. Most GPS devices are the quality today touch screen, so in any case, and you should check the sensitivity of the screen before the purchase.

Battery life is another thing. You would like to have your GPS sufficient battery life to last longer journeys. Most good GPS systems today have a car charger. the average is 4 to 7 hours of battery life. Then you must also make sure that your GPS provider on the cards in your country has.Very often, faulty, incorrect and inconsistent maps lead disasters to navigation!

It is always better to choose the a lot of fun has features like photo memory and mp3 playback a GPS. Bluetooth functionality be able to synchronize your Bluetooth enabled mobile phone for hands-free.

Finally, the price is. The best GPS device would be either too cheap or is expensive, but one, which offers all the features that the GPS device at the same time a true pleasure, without forcing you, those are. The easiest way to overcome the angle of the price is a budget and stay there.

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GPS in India written by: Sanjeev Walia

2011-09-18T13:38:00.000-05:00

Number of views: 137 view (s) India has a long way gone in the past 20 odd years. From a country where technology is reaching the homes of only a few privileged, is, it has become a nation, where has accepted any technology as a part of all aspects of their daily lives. Today for farmers in remote villages always information about better agricultural techniques from the Web. Mobile phones ringing in the pockets of the Indians in cities, small towns and villages. Not to mention from which the Indians day in, day out see hundreds of different satellite channels.

It is however, shocking and disgraceful that the country has still not warmed to the excellent and very useful technology GPS. What is GPS?, could questions. GPS or positioning system global is a worldwide radio-navigation system consisting of a constellation of 24 satellites and their ground stations. The system uses satellite mapping of positions of stationary or moving objects on the Earth quickly and accurately.

Many Indians can use GPS to improve their lives in many ways great. Are position of your vehicle or the whereabouts of your employees business owners concerned about the? GPS is the solution for your. Concerned parents want to location of their young in this fast and crazy world monitor can do easily with the help of GPS. Also mobile phone owners who like to protect your expensive mobile phones from theft can seek and their instruments in a snap with the help of take back the this amazing technology. Lost in a new city? GPS shows you the way to your destination, but removed it can be! Furthermore, can the miracle technology in social applications of the police or medical services.

The rich benefits of GPS will see the rate of this technology by the West, sooner or later is bathed India. Soon, it is bound to give households and offices in the entire nation. And why not, it is finally to make a cheap and effective way of business and private life safer and better.

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Search for your fleet movement discreetly written by: Sanjeev Walia

2011-09-18T09:38:00.000-05:00

Number of views: you are a company with a fleet of trucks or buses carry out your commercial activities 113 view (s)? You need to search for effective fleet management system for growth of your business. TRUCKS and buses are valuable assets of your company and protection must against road accidents and kidnapping, of course, your concerns. Most are accidents by rash and careless driving causes. GPS-enabled fleet tracking system is a blessing to modern commercial vehicle owners. It helps to locate your fleet movement.

GPS fleet tracking systems are very effective in public transport, in particular a fleet of commercial trucks, school buses or metered taxis. These systems help the undertakings concerned or the school management to know the exact position of a particular vehicle. It improves the safety of the vehicle both its passengers. Drivers of vehicles with GPS enabled devices are in a position, the necessary adjustments in their route against overload traffic problems. Efficient route management helps save fuel and vehicle maintenance costs. Many schools and business houses opt to install GPS tracking system in its fleet of buses. This gives peace of mind to official Institute and family members of passengers. This technology has helped, very way into discrete location of your fleet movement.

On an experimental basis, a private taxi company introduced back enabled some years, GPS metered taxi service in Mumbai, India. Can the customers the taxi phone book and select it up in a privileged place. Leaves a passenger by mistake, some personal element in the taxi, can it be easily using the APS technology. Encouraged by drivers and passengers with overwhelming response, the company significantly to increase the fleet size in the very near future plans.

Latest vehicle tracking device based on the global positioning system (GPS) technology is installed on a vehicle. Vehicle tracking is done via satellite. Because the satellite transmits the information signals of an electronic tracking device to the computer via the Internet. The person in the control room can access this information at the desired time and keep a close eye on the movement of each vehicle of fleet move outside.

Global, a technology developed for the US Army is positioning system (GPS). It was later in the commercial market moved show good results in the pursuit of commercial vehicles. GPS tracking system helps in monitoring the speed of the vehicle, keeps a check on the route followed and a total distance of a specific vehicle. GPS fleet tracking systems are very effective in monitoring the driving style and the speed of the vehicle. It the fuel also helps maintain usage records, so keep a check on fuel and maintenance costs. GPS fleet tracking system has certainly helped associated with vehicles in increasing efficiency and productivity in companies. It not only in cost and time savings helps, but also proved a very effective system in discrete location of your fleet movement.

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Should you install a tracker on your Childâs phone? Created by: Sanjeev Walia

2011-09-18T05:38:00.000-05:00

GPS articles
Should you install a tracker on your mobile phone child? Expert author: Sanjeev Walia word count: 504 words

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With the TomTom XXL 540TM portable GPS Navigator you must never questions, for the way again written by: Kenny Kings

2011-09-18T01:38:00.000-05:00

GPS articles
With the TomTom XXL 540TM portable GPS Navigator you will never need to ask for directions again by expert author: Kenny Kings word count: 579 words

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GPS makes fishing more efficient and more secure posted by: Sanjeev Walia

2011-09-17T21:38:00.000-05:00

Number of views: 106 view (s) are you planning for corporate fishing events? Are you concerned about your safety, if your livelihood is? GPS is definitely the technology for you. The objectives of each fisherman are back home safe and the largest haul fish catch. With GPS on the fisheries, not only fisheries makes safer and easier, but also filled with fun.

If you are really concerned about security, you need to be in any case, go for GPS technology. If you get on a fishing trip, fog, darkness or bad weather you confused about your start point or direction. If you use GPS, it is easier to search the House point or the starting point. Once in the water for fishing to get, simply select your location from latitude and longitude and record in the GPS device. GPS is the itinerary followed in which allows fishing point of return home in right direction also for confusion due to weather problems. For corporate fishing events if Fischer in group work, if you get lost, send the coordinates of your location to your fellows. Coordinates can find your location easily by GPS tracking them.

Use of GPS and only catch more fish than the next man! GPS can be used to find the fish easily. Once you catch fish at some specific point and you feel that rich fish it, mark on the ground in the GPS device. Collect all the points in the device locations of this. Use these spots for fishing during your next trip. Mark also a circle in the center of the Group of points as a Center for the decision, your fishery for future travel with the help of point. The probability of the fishing in this zone will be higher. You can also get GPS devices to the weather of the day, fishing can be used.

So what you waiting? You invest a nominal value of GPS fishing device for and a lot back.

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Determine the correct Garmin Nuvi GPS system for your needs written by: Paula Smith

2011-09-17T17:38:00.000-05:00

GPS articles
Determination of the right of Garmin Nuvi GPS system for your needs by expert author: Paula Smith word count: 617 words

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Magellan GPS RoadMate 2200t by written: Tommy Hansen

2011-09-17T13:38:00.000-05:00

Number of views: 44 view (s) the Magellan GPS RoadMate 2200t offers most of the latest features, such as text-voice features and multimedia capabilities in a modern device. Plus, have you add the choice are located, targeted traffic updates, as well as topographical maps for outdoor use.

The Magellan RoadMate 2200T features a new, small layout and includes also two helpful tools, known as QuickSpell, Smartdetour, and, in connection with easy navigation. It measures 3.7 2.0 from 0.6 in. and also weighs 7.8 ounces for easy transport between cars.
It has also an exact recipient, text-voice performance, music playback, as well as an image viewer.

Magellan GPS 2200t is lightweight, very portable, fast, and the screen is fantastic. The unit is even fast tracks very quickly, and also the satellite acquisition.

The actual RoadMate 2200T can easily calculate that routes, on the basis of four methods: a very short time, at least, rent use of motorways, and the most use of freeways. With all the options, you can also teaching the machine to avoid toll roads. If you are planning an extended road trip, read the trip planner function system multiple sites. Ticket-travel PC, which informs your average speed, travel time, travel time and total travel distance, if you are in this kind of thing.

The actual 2200T is text-voice calls, SayWhere, although Magellan. The technology allows the device specific brands speak Street if voice guided directions, which may well give you your face travel time instead, to get the GPS screen. You will receive schedules in 3D, 2D and text-based directions, and you look at.

2200T consists of music playback and photo viewing. The music player supports MP3 and WMA music files, and you produce and change also playlists. In addition, there a great equalizer, with which you can optimize the actual sound, and repeat and shuffle modes. The picture viewer supports JPEG and BMP images.

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The hurricane Irene published an interactive map of ESRI

2011-09-17T09:38:00.000-05:00

29 August 2011

ESRI published an interactive map that allows users to constantly updated Hurricane view information. Users can track certain hurricanes and see their projected path and also access news feeds, precipitation, and storm, wave information.

ESRI, the hurricane, the RSS feeds of the rainfall, every 15 minutes are supported updated, and the storm surge, often the greatest threat to life and property of a hurricane, updated every 20 minutes. Click on the image below on the interactive map.

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CoreLogic analysis shows more than 35 billion dollars in potential exposure to property damage in New York City and long living Iceland of Hurricane Irene

2011-09-17T05:38:00.000-05:00

29 August 2011

CoreLogic published data show potential exposure to residential real estate damage from Hurricane Irene storm surge flooding of New York City and long Iceland. Assuming that Irene reached category 1 status, damage could be more than $35 billion in total. For example, a category 2 status, storm damage increase could potentially a total of $59 billion and Irene category 3 state reached, damage could exceed 88 billion dollars.

The CoreLogic analysis measures damage caused by the storm surge and includes associated with any potential damage caused by wind and rain hurricanes. See tables below.

Hurricane-driven storm surge can cause significant property damage floods, when strong winds and low pressure caused to collect water share the powerful rush of land on the storm, when moving the hurricane on the Bank.

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Ago out: the good, the bad, the incompetent

2011-09-17T01:38:00.000-05:00

Today, the most efficient use of the spectrum of the world has seen more than a billion people per benefits. Two billion morning when modernised and interoperable GNSS is real. This massive installed base is an innovative advantage, and with good will of inestimable value for the United States.The the latter arises from the high degree of confidence in the United States and deal with GPS, one of most successful - and perhaps only - simultaneous foreign aid and national economic programs ever created.

Smooth dealers within a hedge, operate play with other people's money, billions of raids of this national resource for video on mobile phones, want to make young audiences.

The Federal Communications Commission has acted the ways, with reasonable expectations of a federal agency rules. There was early with the appearance of the LightSquared agenda, the issue of a decision to buy inappropriate speed.

It has refused, explains and show opportunities, one of extreme ignorance of the radio frequency (there are conflicting reports whether agency technical staff was always consulted by leadership prior to the accession to the LightSquared request) proclaimed was - and too clever by half. The Chairman, in the line for which was China according to rumors, was careful not to sign the waiver, but the Act of a child have done.

In this law, she ignored conflicts in two competing national policy objectives: the national space policy and the broadband memorandum. Rather than spending the time take to bring important principles in line, is the lack of its own course.

The row which got President lean out of the window, and now must find a solution, which allowed him, again before the election to crawl the Agency. Either that, or he and his advisers, including the FCC Chair will knuckle down and carry on regardless, political saving face in the short term during the national infrastructure and defensive skills.

Politicians never underestimate want to save face. In many ways, it's all what you have.

The best thing the GPS community in this quiet reloading may period is to keep the letters and calls to the Congress: the most secure and fact-based is the FCC, that the terms and conditions for the LightSquared waiver does not meet a requirement condition and withdraw the license terrestrial network in the 1525-1559 MHz band. This is the only approach, fully in line with the national space policy and the broadband memorandum, as well as the FCC own arrangements.

At this point, subject to any action, the policy considerations unpredictable by the FCC.

Gunfight in the Cantina.

About the author: Alan Cameron to Alan CameronArticles by Alan Cameron

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Advice: explore the technologies behind location-gate

2011-09-16T21:38:00.000-05:00

For the past few months has controversy raged about the revelation, the Apple, and Google mobile subscribers able to track movements and, where it may be vulnerable to hackers and other inappropriate use stored this information in an unencrypted file to the handset. The resulting location-gate scandal underscores sometimes control the mobile subscriber information against the business goals of the dominant platform and applications providers. Immediate revenue opportunities from the Subscriber can these business objectives pursued or wider self-interest initiatives such as such as collecting data, the valuable to third parties such as advertisers or building notified subscribers Wi-Fi access point databases.

Furthermore, while much about the privacy implications was written the collection and use of information of consumers location, some articles have clear rules the technologies behind Apple and Google tracking activities. It is important to fully to explore and understand that these technology methods, and how she used from other location technologies, to correctly distinguish the threat through location write a review and to develop responses to protecting the privacy, at the same time the advantages of location based services.

Location, tracking and storage

iPhone and iPad subscribers had been previously aware that Apple has their location via GPS, because the company notified subscribers when an application needs, asked the use of GPS position to identify, and they, opt - in. However soon after able gate, had Apple's Vice President of software technology, Bud Tribble, told Congress in May 2011, that Apple also device locations over a period by using of triangulation between nearby Wi-Fi access points and wireless base stations was persecution. Triangulation is the moderately accurate way in which the mobile device measures close to nearby cell site or point identification and may signal strengthen, typically determining device location within a few hundred meters.

After this revelation was Apple's first answer, that "users are confused" and that it was simply "manage a database of Wi-Fi access points and cell towers to your current location... to help, your iPhone quickly and accurately calculate the location if requested." Soon after Apple site tracking activity was revealed, it was announced that Google was essentially the same, albeit to a somewhat lesser extent (Android phones do coordinate only the 50 latest updates and up to 200 Wi-Fi access locally stored locations), and a similar triangulation method without explicit knowledge of the participant. Google Android devices also have GPS ability.

Why, if both OS vendor embedded or used GPS in their phones, would access a less accurate location method of triangulation?

None of the companies has given an answer. We know that the triangulation method of less battery power than GPS, conservation of battery life for other uses when filling out performance holes for GPS in urban and indoor environments used. Also, in contrast to using GPS, mobile subscribers are either unable, triangulation or disable must, separately. More important is the fact that allows the OS vendor location automatically identify triangulation and monitor it during the time in the background without the knowledge of the participant, such as building and maintaining a database subscribers the Wi-Fi access points reported.

From the perspective of privacy is a dramatic difference between monitor the situation in the course of time (the bread crumb trail, that Apple and Google used), the position for a particular purpose and handle the location information only within the limits of a secure wireless network. Useful applications that are accepted as such as E911 situations, safety-of-life, General, deal with the latter method.

Other players in the mobile ecosystem, such as for example wireless network operators subscriber information location, as well as put together have to save files in the same way that Apple and Google have but not through it into the device as historical. Some information on the side of the network in connection with billing records for calls (also known as detail records or CDRs) is present, but this is not bread crumb track of cell IDs. E911 calls records that never one for the use of public agencies, but most users E911 call. Contains other messages, rough location may be on a temporary basis (such as location updates field) available, but these are usually not aggregated or stored for later processing.

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Meizu Smartphone for China contains u-blox GPS

2011-09-16T17:38:00.000-05:00

The GPS chip of u-blox UBX-G6010-ST is at the heart of the latest M9 Meizu multimedia smartphone with GPS. For the Chinese market, the M9 has developed a high-resolution 3.54 inch display with 16 million colors, multi touch support, Web browser, camera, HD media player and 3D games. It includes also out-of-the-box-GPS features such as Navigator, digital compass and accelerometer. A library of location-based Applicationss can be downloaded from Google's Android market, online.

"The slim, lightweight M9 is our second generation smartphone delivers interactivity, displayed high-performance applications and vibrant media, that consumers in China demand," said Mr Huang Botiao, Director of Meizu, "This includes a wide range of compelling location based applications and services that require the highest performance GPS receiver." For the M9 u

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Telogis as one of the fastest-growing private companies in United States

2011-09-16T13:38:00.000-05:00

30 August 2011

Telogis Inc., a platform for location intelligence, appointed Inc. magazine to a fifth in a row on the Inc. 5000, a ranking of the fastest-growing private companies in the nation. The list provides a comprehensive look at the growth of America's independent entrepreneurs. Telogis ranked 728th, on the list with 434 per cent growth from 2007 to 2010. The company, known as the 59th fastest growing software company and the 54th fastest growing companies in the Los Angeles Metro place.

Telogis offers a powerful Geospatial Platform for software development and a complete end-to-end platform of software-as-a-service (SaaS) applications, the company said. Is Telogis working business decisions with major companies around the globe, as well as small fleets with premium technology and services, reducing operating costs, productivity and security, and give them help to medium-sized enterprises, outfit formed based on real-time data. The company works with some of the largest OEM in the world and mobile interface technologies to offer their customers advanced telematics, vehicle scheduling and optimization, mobile workforce management.

Companies that have a report on this year's Inc. 5000 list 350,000 jobs created in the last three years, and achieved total sales $366 billion, 14 per cent over the previous year under the winners. The full results of the Inc. 5000, including company profiles and an interactive database, by sector, region and other criteria can be sorted, see www.inc.com/5000.

"Now more than ever, we trust on the Inc. 500/5000 companies and innovation to advance, jobs and drive forward the economy", Inc. magazine says Editor Jane Berentson. "High-growth companies, not large companies are where the action is."

"We are working in a very versatile and highly competitive market," says Dave Cozzens, CEO, Telogis. "We are honored that the tireless work of our team and their contribution to the success of our customers from the Inc. 5000 is detected again." "Our commitment to innovation and the promotion of location-based intelligence solutions can be still our customers with new features while driving also our own growth."

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Happy feet Penguin heads home equipped with GPS

2011-09-16T09:38:00.000-05:00

Emperor Penguin happy feet is finally on his way home to the Antarctic, two months after the first wash up on a New Zealand beach. He will be equipped with a GPS Tracker, before he released, can to allow his fans to his online monitoring. The GPS receiver can stay for up to four months in the place.

The Penguin was sailed the Monday evening in a specially built new box on board the research vessel Tangaroa, NIWA, set by Wellington. After four days at sea it back into the Southern Ocean, East of the Auckland Islands at about 53 degrees South appears.

The Penguin was for cared in the Zoo of Wellington, is, where a popular attraction to Peka Peka Beach in June, ill and confused, he conquered sand have been discovered. More than 1,700 fans came to see from him from the Zoo.

Gareth Morgan and wildlife of tracking company Sirtrack donated the GPS Tracker. Fans will be able to track our far south of the Penguin-progress on the Sirtrack site and the site.

The Penguin is named after a popular animated film from 2006 about the emperor penguins.

The big picture: Why location is hot?

2011-09-16T05:38:00.000-05:00

LBS Insider newsletter Editor Kevin Dennehy hosts a Webinar on September 15. "". The registration is now open for the webinar, will place 10 am PT / 1 pm ET / 17 GMT.

Experience based services, such as the location in 2011 pénale - and what is in store for this potentially lucrative market. Learn what drives the location market. Is the integration of local search, social networks, the market offers consumers Kindle? How is the role of airlines with the growth of competing app stores and ecosystems change? Navigation is used to generate most of the revenues in LBS. Now people to give it away for free. It is it still the market - or is only a part of the infrastructure? Speakers are wireless network operators, handset manufacturers, consultants and other industry professionals.

Visit our Webinar page for more information about GPS World webinars.

Advice: Happen epic - Europe PNT Industry Council

2011-09-16T01:38:00.000-05:00

We have the United States GPS Industry Council, the Council of the Japan GPS, Korean GNSS technology.

All that is missing?

The only large area without a uniform industry nexus, where can such challenges is the challenges for the community, based inter alia on GNSS performance, navigation and timing (PNT) are always more numerous and complex, and Europe. However, this is to change.

Out of my background and current activity as CEO of DW International have a standalone navigation consultancy with a strong interest in GNSS specifically, I started the European PNT make industry to trade Council (EPIC) with other industry leaders as the focal point for the PNT community concerns and to help to coordinate the effort of standardization and harmonization. In addition, it is issues such as the LightSquared debacle threatens key, that the parties in Europe have a voice on the international stage.

A recent study, carried out the emerging epic together with Marketing Analytics the need for an organization such as EPIC. We asked PNT key figures around the world on the issues relating to them and how should addresses these concerns by EPIC. For such a diverse group of respondents (including representatives of transport authorities, academic institutions, OEMs, independent consulting firm, land survey companies, maritime, and aviation) there was clear agreement on the need for a European place PNT facilitating better interoperability and harmonization of standards among the current PNT activities, carried out all over the world. Sixty-six percent of respondents wanted an international forum for the exchange of information (i.e., ideas, best practices and teachings) where such issues such as interoperability and harmonisation can be treated.

63 Percent questions as a very important issue for EPIC rated PNT system-level, although with 56 percent for PNT standards in the areas of air, rail and E112 evaluated as very important. There is no shortage of problems to tackle, and EPIC is as a major player in the formation of coalitions that are required.

As a respondent, its priorities PNT policy asked:

Galileo launch schedule; information about GLONASS L3 and GLONASS CDMA compass CPII and CPIII plans, particularly the ICD and the frequency of the scheduled L1 CDMA signal signal information and operational plans;SBAS plans, such as EGNOS and GAGAN.European regulatory plans, which aim for navigation and location; E112, road users charge tracking and logistics;Standards for navigation and location of applications and applications that use a position.

What the attractiveness of a forum for the exchange of technical know-how among experts, it was also clear that the respondents epic to act as well as wanted. You wrote:

"EPIC must result/results oriented, and not in a talk." "Therefore issues such as LightSquared set up head, so that bureaucrats listening, the science behind the decisions and guidelines as a commercially operated for the short-term political expediency."

In fact, EPIC joined the choir of the organizations, directly to the FCC call for a rethinking of the LightSquared output.

Personally, I think that with industry active in the United States and Asia, EPIC is the third leg of the stool. PNT is that large international organisations risk lagging, except where their interests are represented such a dynamic world, with so many moving parts, and the information they need, is in a consistent and practical way.

But more than that, PNT is a utility that be protected must be maintained, improved and used. EPIC makes sure that those who want to can.

It is. The participants are there. It is happening.

About the author: John Wilde about John WildeArticles John Wilde
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Advice: Cloud-based location changes enterprise field

2011-09-15T21:38:00.000-05:00

New technology and mobile operator openness now provide real time access details on phone location for the company with no application on the mobile device required.

Yes, that's right: the application required! Cloud-based situation, offered through direct connections to wireless operators, is changing the playing field for companies to introduce immediate operational efficiency. Able to marry insight offers privacy control and flexibility, cost savings and time-to-market benefits company multimodal communication over network application programming interfaces (APIs). Whether providing geo-targeted offers, services, review the activities of workers or other location to perform delivery, relevant actions companies now cross-carrier access to site information for more than 85 percent of U.S. wireless subscribers have immediately!

This allows app-less go the company without costly and time-consuming deployment and maintenance of cell phone applications. In addition, no special hardware is required. Location by carrier networks ensures secure and tamper-resistant delivery site information, because no potentially hackable client software in the production or delivery of this information is involved in. It comes directly from the carrier network through secure connections.

Cloud-based deployment, such as on the location platform, TechnoCom opened location intelligence to all types of devices, including smartphones and feature phones. This is a major barrier that exists with the existing Smartphone only applications and allows companies, their workflows and business processes that the real time starting point for a secure knowledge and adapt immediately take advantage of reliable source. Development cycles and costs are a fraction of the required for Smartphone applications, such as download droid or iPhone apps, and the adoption hurdle of user's initiation is eliminated.

Simplification of access and the provision of paving the way for the introduction and finally opens the floodgate for location based services are implemented in all wireless networks on a large scale. The turning point is this, that cross carrier text had acceptance messaging access and interoperability on cellular text messages in the 1990s.

Through the use of technology, much like in the carrier networks and proven for use in an emergency 911, benefit companies immediately when new data become available from wireless operators, such as device capabilities, presence, tariff-plan status, roaming status, etc. Companies can necessary, immediately use this insight with upgrades to its server applications, and no new technology deployments in the field. That offers companies a huge return on investment, even integrate and consume extensions dynamically. Location from the cloud opens up a new, instant intelligence border that use not for business was possible only in the last year.

This unprecedented access to location information has a responsibility for compliance with the industry recognized privacy of controls. To do this simply to companies that are not experts in such a policy, TechnoCom offers location platform approved airline data protection management features, and we work hand in hand with our customers, to ensure that their implementations in accordance with the recommendations of laid down CTIA.

Development situation of other media such as VoIP, will further increase access Wi-Max, NFC, Wi-Fi the ubiquity of cloud-based location. As devices become smarter and more powerful, better communication and device intelligence companies are positional awareness to the yet another level of efficiency when interacting with their mobile users, workers, and the assets to catapult.

Mario Proietti is co-founder and Chief Executive Officer of TechnoCom Corporation and a member of the Editorial Advisory Board of GPS World magazine. He has a master's degree in electrical engineering from the University of Southern California. TechnoCom provides cross-carrier location services company due to its location platform Web services APIs. The company also wireless networks, products and software location integrates technologies and works to enable wireless operators E911 with location based services.

About the author: Mario Proietti of Mario ProiettiArticles of Mario Proietti

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Locata: A new constellation

2011-09-15T17:38:00.000-05:00

"GPS can develop more quickly enough." Satellite-based systems maintain that now for the can not speed of development, hyper fast evolutionary step of modern applications and devices required. "To position, for the future very become clear that GPS is now a terrestrial component."-by prospectus Locata Corporation

"Billions of dollars to try a large number of companies and engineers to improve the GPS in urban and indoor applications have raised," explains co-founder Nunzio Gambale Locata Corporation. "In view of the technological Locata has something completely new: the possibility of a GPS-style to create system independently on the ground."

Of the GNSS community see for themselves even to the Locata coming out party in the ION GNSS 2011, including the publication of a Locata signal interface control document (ICD). GPS world has an advance on the technology in a June the demo, which can see all ION participants. This article provides these reports to an overview of the technology.

The key to the Locata of the positioning system is the signal of the Locata transceiver or LocataLite, its time to synchronize other LocataLites on a network. Locata created a network that "is a near perfect synchronization according to the company," without atomic clocks. Each transmitter synchronized dynamically says with Locata transmitter with a patented method called time-loc Gambale, a Locata to disable network with currently about 2 nanoseconds.

Each LocataLite base station has a continuous series of approximately 10 km, much like a cell phone tower with indoor signal.

The company stresses that its transceivers are not Pseudolites, but also devices, to create the synchronization of TimeLoc, and thus enable an autonomous synchronized network that looks locally, such as GPS. The local constellation is under local control and can therefore for use to any frequency or a density needed be designed by an application makes.

The networks can scale easily. The term "local" can mean a room or warehouse (100 m2), a campus or open cut me (tens of km2), an airport terminal area with approach and landing routes (100 s km2), or a WAN, area or city (thousand km2)

Gambale sees markets for Locata of technology in defense, mining, emergency services, construction and security. An another constellation is used to integrate with existing technology, as simply Locata. This means that a Approprieate GPS Locata receiver the satellite signal when outside of the area can use a Locata network. With a combined GPS-Locata-chip, the LocataLite appears as a satellite.

The company sold its first Locata network in July of 2005. Locata signed partnership agreements of various kinds with Leica of Geosystems and Newmont Corporation (mining), the United States air force, the advanced navigation technology center at the air force Institute of technology, and several other companies under confidentiality conditions. Was a first test deployment to the Hollandia Oman Air Force base in May 2008 both truth over a test range from approximately 52 15 kilometers.

For high-multipath environments like indoor and storage, the latest development is a TimeTenna that will show it in ION-GNSS referred to a new antenna.

Future research and development focus on the miniaturization of the recipient Locata. Started first in commercial and industrial equipment, and finally in consumer devices has such as mobile phones can be integrated on a combined GPS GLONASS-Locata-chip.

Locata plans, with integrators only, not with end users to make the technology of qualified partners, the development of recipients and applications to work. The ICD is the first step in the Locata technology rollout.

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The system: 2 sector takes over second IIF

2011-09-15T13:38:00.000-05:00

Command and control of the second passes GPS block IIF by Colonel James Ross, 50 space Wing Commander, Lieutenant-Colonel Jennifer grant, 2nd space operations Squadron commander.

The U.S. air force 50 space wing 2 space operations Squadron took command and control of the second block IIF GPS satellites on 19 August. SVN-63 (PRN 01) healthy set on 23 August.

The 12 next-generation GPS IIF-satellites from Boeing built have improved accuracy through advanced atomic clocks, a longer lifetime than older GPS satellites and a new signal, L5, which will benefit from civil aviation and safety-of-life applications.

Missile systems Center GPS Division in Los Angeles air force base and the space remained in the control of the satellite in a 30-day in-orbit check-out time before hand out.

Constellation is more robust and powerful than at any other time in history, said the GPS wing. Members of the 2 sector operation the largest Department of Defense satellite constellation on the master control station and a worldwide network of stations and ground antennas.

II part A mandatory recalls. Air force officials want only for the second time in a quarter-century back to Active status to convert a disused GPS satellites. 2 Sector employees in late noticed can, starting the clock on the GPS IIA was SVN-30 to malfunction. Engineers and counterparts Boeing and Aerospace Corp. 2 sector developed a plan to SVN-35 in service to replace the ailing bird. The 18-year-old satellite was provided from active service in 2009, make room for the actual deployment of the latest GPS Block IIR the vehicle out of service; However his navigation signal continues to function properly.

"We in-orbit spare parts hold for exactly this purpose", said Lieutenant-Colonel Jennifer grant, 2 sector commander. "The flexibility, replacements like this with minimal impact to the global user the robustness of our current constellation and the recent completion of the expandable 24 provide architecture us perform."

OCX hits bump: no preliminary examination pass design

The the recently completed first preliminary design review (PDR) were the next-generation GPS ground control system (OCX) led by prime contractor Raytheon does not.

Not passed this critical PDR control, as early in the OCX process and in the current fiscal environment (Congress has cut budget and move elements on the right to modernise already are.), is a blow for the GPS modernization efforts. It adds the concern about the OCX GPSIIIA gap with GPS IIIA produced with the Lockheed launch space vehicles (SVs) and payloads, which are planned to start a full SS-months before the OCX-ground system was originally planned, can control to the start.

Undoubtedly, this timeline extends to the right with this development.

The PDR is a formal control by the Government adoption agency - GPS Directorate of the air force in this case - of the overall architectural design of ocx automated systems and the related C2 software. PDR, critical for military projects, is carried out mainly for the new GPS ground C2 system, to achieve confidence, that the design meets functional and nonfunctional requirements and meets with the General enterprise architecture. Overall project status, proposed technical solutions in the PDR determine developing software products and all associated documentation at a high level itself are completeness and coherence with contractual standards. The PDR is used also increase and to identify any technical and/or project-related problem solving and project, technical, safety, and/or the business risks reducing further detailed design and development, testing, implementation and operation and maintenance functions.

During a PDR, the Government has usually several options on the result. It can be:

ApproveApprove ConditionallyWithhold ApprovalDisapprove or error the program.

In this case, the Government has permission deny and not approve conditionally or formally fail until all PDR action items are checked.

LightSquared errors

For the first time in a few months, there is little of concrete messages report on this subject - as the press date August 24. The Federal Communications Commission weighs its options and questioned the additional data requested it: the number and the service life of the GPS receiver, which will be disturbed, and the number of the terrestrial base stations LightSquared plans provide.

See top story and today's news, also the navigate, survey and GNSS-design & test e-newsletter for latest developments.
Here are the highlights from the "LightSquared-watch"-Webinar on 18 August; Download at www.gpsworld.com/webinar:

GPS is probably the most efficient use of the spectrum, the world has ever seen; almost a billion people benefit, the GPS signal, which is now available. This usage is a large installed base and source of the innovative advantage for the United States. Most importantly, it provides a high degree of confidence in the United States and their maintenance of GPS.
-Scott misinformation is speed widespread and action pressure prior to analysis characterized the early stages of this process. History has been interpreted, and fit the facts distorted to desired reality. We have heard that lawyers supported allegations against the decisions of the engineers - with only the latter of verifiable data.

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Microtechnology is growing up

2011-09-15T09:38:00.000-05:00

The size of an Apple seed: Micro PNT goal (conceptual illustration), a chip timing and inertial measurement unit, 8 mm3.

The aggregated DARPA Microsystems technology for positioning and navigation timing (micro PNT) program pursues a new wave of innovation, the again and again life revolutionary ideas and fabrication technologies for micro/Nano/Pico/Femto/Atto scale packaging, ultra low power electronics, innovative algorithms, never explored architectures and use the new integration paradigms.

After over two decades of harmonious investment in development, potential users of so-called small technology for positioning, navigation and timing (PNT) applications increasingly questions, "we still there?" Clear, made some significant progress, and we see a footprint of the technology in a steadily-growing consumer electronics market of full interactive products of inertialen and timing of micro techniques enabled. These products include accelerometer for game applications, Gyros for car safety, resonators for watches, and more.

However, the question remains: the technology is really at the level of what we as precise navigation and timing, it is a precision of at least 10 meters in position and 1 nanosecond in time can be reached throughout the duration of the missions, ranging from minutes to hours to days? In fact technology is less adequate for many military applications perform several orders of magnitude short for long-term stability, dynamic range and accuracy compared to conventional technology, which is already known.

Why does inertial instruments and watches lead low necessarily to a reduction in performance?

We have still not even a comprehensive answer to this question, and we are still working hard to refuted the claim that the high performance micro inertial instrument is a contradiction in terms. We can make things, small, but we still they sufficiently precise and uniform; the precision Lithography-based production is the 10-2-10-3 (the ratio of the average defect to the smallest size), while the accuracy of conventional manufacturing with precision machining of two to three orders of magnitude higher, the 10-5. We know we can layer by layer with high precision will pay materials, but we can micro devices 3D really as accessible with conventional processing is easy. We have an excellent case for low-cost and bulk import consistently production, but we can challenge seriously, so-called boutique processes, when it comes to reach the precision, structural complexity and long-term stability.

We need the stability materials new knowledge about. We need also a better understanding of the material scale surface effects, energy loss mechanisms and the consequences of making imperfections on the performance of micro instruments.

PNT applications require exceptional new manufacturing technologies and new materials with special properties. To achieve the phenomenal accuracy for precise navigation and timing, we need a new wave of innovation in design and refinement of the many existing converters. Probably future breakthroughs in Microtechnology for PNT are still used on physics, new materials, highly specialized manufacturing technologies and batch Assembly techniques, selective wafer-level trim and polishing, implements a combination of passive and active calibration techniques strategically correct on-chip and introducing innovative testing technologies.

The need for advanced features

PNT-technology-use has doubled every five years since 1960, GPS and the miniaturization of electromechanical components. Future using to PNT every two years from the telecommunications, automotive navigation, robotics and other commercial markets, insert, micro electromechanical systems (MEMS) technologies, double-click. The modern paradigm of PNT is based on the assumption, allows the space-borne GPS every user on the same reference system and timing standard is available to provide the most of the time, position, speed and timing information.

Today's military systems more and more users rely on GPS, create a security vulnerability for United States and allies dismantled war-fighters, GPS or deny. If GPS is critical information regarding the position, orientation, inaccessible, and timing can be collected only by an independent integrated instruments: a local clock and two triads of the inertial sensors (three acceleration sensors for position) and three gyroscopes for guidance. The ideal solution would be a stand-alone instrument does not rely on the external. Microscale precision watches and inertial sensors are committed to the paradigm of the stand-alone PNT address.

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About the author: Andrei M. Shkel of Andrei M. ShkelArticles of Andrei M. Shkel
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GPS, exact positioning with integrity

2011-09-15T05:38:00.000-05:00

31 August 2011

Brad Parkinson, the first Director of the Office of GPS joint program has a presentation, government officials and personnel to the differences between communication and navigation, to educate and why the GPS community so persistently is threats to the integrity - and why should be fought ruling in a similar way. The presentation is available here. Parkinson's disease includes includes "it is unthinkable to many, to understand that the GPS applications, and the national dependencies the the Federal Government: would seriously consider, authorize jammers that could such damage to the country."

And yet....

The presentation refers to the fact that "integrity is the cornerstone for the most high productivity applications, such as: aviation, heavy vehicle control, automatic mining, surveying, auto agriculture." LightSquared threatens GPS availability, accuracy, and, most importantly, integrity.

Parkinson continues to shed light on the difference between digital communication and digital navigation. "they are superficially similar, but there are fundamental differences that must be understood."

In digital radio communications:
Message inbound • is not known, this is the crux of the finding-
• Must determine whether any signal of "Bit" is an or a NULL
• Use sophisticated methods to resolve errors

In contrast to digital radio navigation:
Signal incoming • sequence (ones and zeros) user is completely known.
• The goal of the user is exactly the transition from one to zero (zero to one) time

Without noise, a narrow band receiver would give consistent results. Unfortunately, the GPS band is dominated by natural radio noise. Natural radio noise caused much uncertainty in NULL crossings for narrow-band receiver

To achieve the maximum precision, has the full-band GPS receiver "sharper transitions," reduce the effects of noise and enables a more precise measurement of timing. So, the full - band GPS receiver sub-meter allows accuracy and the substantial productivity gains of the U.S. in agriculture, construction and machine control.

Why does the high performance GPS need full band GPS receiver?
Full band, improves the timing uncertainty of basic GPS measurement up considerably. This is important for the Sub meter accuracy, which is the basis for many productivity-enhancing applications with $10 billion in annual savings s credited. Full band GPS is much like a fine telescope: without full-band, the signal not well focused

Why the GPS community so immovable, additive noise (26% more noise makes) is 1 dB, is everything that what can be tolerated? Because of proposed 6dB LSQ four times the noise makes means: this relates to all satellites in view. Th result is significant damage timing the code transitions and much reduced precision. Another result might be complete loss of lock on GPS signals. It would also significantly extend the time to achieve "first fix."

With double noise amplitude (6 dB more noise makes), have full-band GPS receiver accuracy substantially impaired. A leisure-GPS users (mobile phone) some degradation could - tolerate if he can ever receive. The precision user has no such width.

Parkinson's is on difference view of distribution models to explore, and concludes: to ensure the navigation in the errors, the GPS must take the lowest damping of the interfering signal. This is in contrast to a communication Designer, who must take on biggest cushioning. Can these differences are often at least 10 times to 20 times or more

Parkinson's general conclusions:
It is unthinkable to many, to understand that the GPS applications, and the national dependencies that the Federal Government:
• Would seriously consider authorize jammers that could such damage to the country
• Make would be to prove that they are infringed, the load on the GPS community you
• Would a private company repeated its intention to change and force the GPS user community, again re-prove tolerate damage.

Our banner should "not have the availability and integrity of GPS destroy." "It is the GPS infrastructure important."

Stroll the bones

2011-09-15T01:38:00.000-05:00

September 1, 2007

Happy rolling stones
Hard Kampf
Tales of brave Ulysses cream
Southside Johnny and Miami Steve broke piece man
Soul kitchen doors
No live-performance video available. There is surprisingly little live recordings of Jim Morrison on the Web, with or without pants.
Please Mr. postman Beatles
My Sharona talent
Lola kinks
Payday-Jesse Winchester
Not Jesse but a right competent, elegant cover band. Shoots inherent in the song at the gate but the stamp.
Seventh son of Johnny Rivers
Nothing lives except a Georgie fame version in 7 / 4 Whooeee. So, we went on ya new age.
Lip service Elvis Costello
I would like to go there
So that a rock ' N want to ' roll star Byrds
The older guys who tell me what is it at all. The older guys have developed really all there.
Route 66 rolling stones
Turn on your Lovelight Rhythm Kings
Cinnamon Girl Neil Young
Not with crazy horse in this clip.
Shotgun www.youtube.com/watch
Junior Walker and the all stars
Meet me boys on the front of the wild Tchoupitoulas
Next findable, this is the big Chief of meters/Neville brothers, backing band for the recording of Tchoupitoulas.
Sweet little rock 'n' roller Richard Thompson and bundle
Actually done here by some other Buncy of naughty boys.
Memories of Leonard Cohen
This be done.

Sarantel WINS defence contract for body armor antennas

2011-09-14T21:38:00.000-05:00

1 September 2011

Sarantel, manufacturer of high performance antennas for wireless applications, production orders for its highly integrated SL1206 GPS antenna for a compact radio system obtained, in body armor, which is embedded for the soldiers. The agreement could revenue of more than one million dollars per year.

Sarantel said the agreement "has the potential" to revenues of more than $1 million per year over five years. It is one of the largest of the company to this day. The product was developed by a European company, which provides a variety of defence and internal security products throughout the world, Sarantel said.

David wither, Chief Executive of Sarantel, said: "this is one of the most important defence contracts Sarantel the company secured until today and the third great military sales in the last four months received has." This deal is an another great endorsement Sarantel of technology in challenging, performance critical applications.

"This milestone treaty will profit expected to be a longer time, which have significant impact on our sales."

Hemisphere GPS releases A31 precision beacon antenna

2011-09-14T17:38:00.000-05:00

Hemisphere GPS today released the new A31-antenna. Offers to use Hemisphere GPS popular Crescent and Crescent vector L1 receiver, the A31 improved 300 KHz lighthouse and L-band (OmniSTAR) reception and excellent GPS L1 multipath mitigation with superior noise rejection, said the company.

A31 is a multi-band (GPS L1, SBAS and L-band beacon) accuracy antenna for use with the most accuracy to receivers suitable tracking of GPS and differential correction signals. When used in conjunction with a hemisphere GPS A21-antenna function A31 and A21 as a suitable position sensor pair, the performance of the Hemisphere GPS VS series vector products improved. The A31 antenna tracking by GPS and differential correction signals in high electrical interference and interference environments are managed, so the company.

"The A31 antenna our ability, DGPS overall performance, continuously to improve", said Walter Feller, senior director of the Hemisphere GPS precision engineering. "Due to increased accuracy and functionality, A31, our clients can more of our Crescent and Crescent vector GPS receiver."

The A31 rated waterproof housing has a robust, IP69K and is 100% maintained. The A31 is marine ready with a standard 1-inch taper reducers mount, that 5/8 inch mounting thread can include also a survey.

The A31 is through the global dealer network Hemisphere GPS precision products. For more information, visit www.hemispheregps.com/precision.

Article from 2000 predicts controversy LightSquared

2011-09-14T13:38:00.000-05:00

6. September 2011

An article in the GPS World published September 2000 problem seems unusual looking ahead and also relevant for the current LightSquared controversy. In particular a passage reads: "with one single makes level, as the criterion for the decision on the release ignores the special features of GPS and possible future GNSS with geometry dependent properties." "Therefore, it is with a specific measure for GNSS release not recommended for other systems in this band or elsewhere."

A copy of the full text of "GPS spectrum: sharing or intervention?" by Steven Lazar, Srini Raghavan and David Turner, the (then) Aerospace Corporation, click here.

Law in the United States applauds reintroduction of FLAIR MAPPS

2011-09-14T09:38:00.000-05:00

7. September 2011

MAPPS announced that cadastre to inventory all federal real estate to develop make an invoice, a current, accurate Federal in the Senate, praise from the National Association of private sector geospatial companies was introduced.

The Federal land asset inventory Reform Act ("FLAIR"), was S. 1153, June 7 from U.S. Senator Orrin Hatch (R - UT) and Mike Lee (R - UT) introduced.

In a statement describing the Bill, said Senator hatch white "everyone, that the Federal Government is the nationwide largest landowners." In fact, they have more than 60 percent of all land in Utah. Incredibly, but nobody knows exactly how much the Federal Government has, because it does not hold is a precise inventory which can and led to waste and bad management. "This law requires the Government to existing technology use to this problem by developing a single, uniform, database an end set, identifying all federal property." Luke again, "it helps to know the Federal and national Governments, which are available for sale and how much energy and other resources on these companies for the development are." "It will also save to to track taxpayer money by eliminating the Government currently based more inaccurate as a result of two lavish and duplicate databases, which the real estate."

An accurate inventory of land owned by the Federal Government was recommended by the Government Accountability Office and the National Academy of Sciences. The FLAIR of these recommendations implemented, as well as calls for an inventory of the existing inventories to eliminate to save reproduction and tax dollars. In testimony before Congress in 2005 Minister of the Interior Gale Norton said the Interior Department alone has more than 100 other property management systems.

MAPPS Executive Director John Palatiello expressed deep appreciation for the leadership of Senators Hatch and Lee. "Mr. Hatch and Mr. Lee with many participants introduction of this important federal legislation work." MAPPS commends Senators Hatch and Lee and looks forward to the cooperation, the FLAIR-law to adopt, ", said Palatiello. Have previous passing of the law of FLAIR support of organizations like the American Congress of surveying and mapping (ACSM) and the national States geographic information Council (NSGIC) acquired. "The law would set a multi-purpose cadastre or an interoperable packet based geographical information systems." This is a good example of an opportunity for ' map once, use many times ', ", said Palatiello.

MAPPS members the FLAIR act in Congress promoted West during the Association programs Annual Conference, held March 15-16 in Washington, DC by meetings with members of Congress and staff. In April representatives Ron kind (D - WI) and Rob Bishop (R - UT) Companion House Bill, h.r. 1620, and the cross-party won agreed representatives Jason old Al (D - PA), Earl Blumenauer (D - OR), Bruce Braley (D - IA), Jason Chaffetz (R - UT), Mike Coffman (R-CO), Gerry Connolly (D - VA), Cynthia Lummis (R - WY) and Todd Platts (R - PA).

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Iridium provides new products and services

2011-09-14T05:38:00.000-05:00

7. September 2011

Iridium Communications Inc. today announced its vision for the future of personal mobile satellite communications, Iridium power. Five principles lead the Iridium-force strategy, including awareness of site enable. Iridium GPS location based services for on-the-go location-specific applications and personal security features integrated, the company said. Other teachings are connections for partners in a wide range of services, simplification with Wi-Fi enabled devices such as Smartphones, and open and licensing their core technologies for working with innovators.

New product and service offerings, which will be announced today with Iridium power are language and products, Wi-Fi products and LBS data offered. The LBS offerings include Iridium tracking portals, where customers can place monitoring, messaging and security tools enabled by the extremes of Iridium satellite phone access. Developed customized online tracking portals create Iridium more than 17 partners with Iridium of the open software platform, the company said. Portal include an Iridium extreme user's real-time status and location of online maps, scheduling regular check-ins, the emergency services, "Geo Fencing," and send the free-form, cans, and social networking messages on street level zoom.

"Iridium satellite-phone industry more than 10 years with the first handheld, commercial satellite phone, pioneer," said Matt Desch, CEO, Iridium. "With Iridium power, we are by an industry transformation again leading significantly handheld connectivity options extend the universe." Iridium is our strategic vision to connect quickly and more people in ways that go never kept - beyond the borders of own devices. Iridium is more than the introduction of a new satellite phone; It means our commitment for powerful new features, including these devices already in the customer hands the Iridium allow network - today and tomorrow. "

For more information about Iridium power, visit www.iridium.com.

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Precision antenna

2011-09-14T01:38:00.000-05:00

Hemisphere GPS
7. September 2011

Hemisphere GPS A31 antenna receiver for use with Hemisphere GPS popular Crescent and Crescent vector L1, the A31 offers improved 300 KHz lighthouse and L-band (OmniSTAR) reception and excellent GPS L1 multipath mitigation with superior noise rejection, said the company.

A31 is suitable for the most accuracy of GPS receiver maintain tracking of GPS and differential correction signals a multiband (GPS L1, SBAS and L-band beacon). When used in conjunction with a hemisphere GPS A21-antenna function A31 and A21 as a suitable position sensor pair, the performance of the Hemisphere GPS VS series vector products improved. The A31 antenna tracking by GPS and differential correction signals in high electrical interference and interference environments are managed, so the company.

"The A31 antenna our ability, DGPS overall performance, continuously to improve", said Walter Feller, senior director of the Hemisphere GPS precision engineering. "Due to increased accuracy and functionality, A31, our clients can more of our Crescent and Crescent vector GPS receiver."

The A31 rated waterproof housing has a robust, IP69K and is 100% maintained. The A31 is marine ready with a standard 1-inch taper reducers mount, that 5/8 inch mounting thread can include also a survey.

The A31 is through the global dealer network Hemisphere GPS precision products. For more information, visit www.hemispheregps.com/precision.

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GPS World files freedom of information request for US gov LightSquared letters

2011-09-13T21:38:00.000-05:00

8. September 2011

GPS world has learned that several federal agencies have official statements to the national telecommunications and information administration of the operational and economic impact of the terrestrial signal LightSquared on GPS services and has submitted, one application of the freedom of Information Act (FOIA) with NTIA, to acquire it.

A source who has seen agency letters, it is as a "very powerful", and stated that the NTIA has delivered none of the letters to the Federal Communications Commission, weigh the matter. This source the NTIA as "sit on it" as part of a "massive bureaucratic game", and further stated that Senator Charles Grassley Iowa and representatives of the Congress "always are efforts to investigate stonewalled the issue by the FCC in their".

Another source, which is dedicated in the Agency impact statements said GPS world, that the NTIA is probably a "Instructions see official reason as part of its deliberative process" to make a recommendation to the FCC. The NTIA is a co-regulator of the spectrum with the FCC, although these last have to say on this matter. This source confirms that they "see letters to the light of love for them."

The GPS World FOIA request calls "All letters by the Federal Communications Commission for additional terrestrial transmission to the national telecommunications and information administration of other agencies of the Government in July 2011 time frame for the LightSquared-waiver sent." "These agencies include, but are not limited to, the Department of Defense, the Department of transportation, Department of Homeland Security, the Federal Aviation Administration, U.S. Coast Guard, U.S. air force, the Department of Commerce, the Department of agriculture, the Department of energy, the Department of the Interior, and the Department of State."

The letters were written by the respective federal agencies in response to a may-tasking of Anthony Russo, Director of the National Coordination Office for space-based positioning, navigation and timing.

Locata passes critical design review milestone for the US air force ground-based positioning system

2011-09-13T17:38:00.000-05:00

Prototype provides centimeter accurate positioning over large areas, if GPS is completely denied 9 September 2011 Locata

Locata Corporation today announced that it the critical design review (CDR) contract phase of an Locata network has successfully completed, with which the United States air force, a ground-based equipment, centimetre exact "truth-reference-level" positioning system for use in environments with GPS denied is. The USAF 746th test Squadron (746TS) awarded a multi-year contract for this project in July 2010, and the CDR was Locata the last milestone before the USAF required a technology demonstration in the United States to be fulfilled. Locata of non-GPS based positioning system (NGBPS) - sold as a LocataNet - provide accurate positioning when GPS jammed more than 2,500 square miles is White Sands Missile Range (WSMR) in New Mexico.

The project major milestone date, shows completion of COR, the company's detailed LocataNet design as the location of the non-GPS-based positioning component of 746TS ultra-high precision reference system (UHARS). The Treaty now moving an initial deployment of about 600 km to WSMR for further tests in October 2011.

"I am excited about the potential of Locata who has technology reference system to improve accuracy in an environment with navigation warfare dramatically our", said Christopher Morin, technical manager for the 746TS on the Hollandia Oman Air Force base in New Mexico. "The Locata team has great progress made in the last year to develop, the hardware and software to keep track of low and medium-sized dynamic flight profiles in all sections of the heights that we are the next generation systems testing the DoD navigation required." The prototype tests carried out in Cooma and reference solution, while the CDR clearly out Locata has and is successful modelling of different sensors, antenna and tropospheric errors. "I expect that the technology demonstration planned for early FY12 enter trust us to field this system throughout the region 40 60 miles from WSMR, that we use system tests for the navigation."

Locata of non-GPS based positioning system (NGBPS) illustrates this technical news, according to Locata:

Proof of the Locata autonomous, nanosecond precision TimeLoc synchronization function if Locata another transmitter (LocataLites) up to 30 miles (50 km) placed will show that TimeLoc "can be cascaded" from a LocataLite to another more "TimeLoc hop" of at least 30 miles (50 km) per hop; viewing LocataLites can successfully at the various high power amplifier to deliver much longer ranges, however, continue to exact TimeLoc transfer, show that Locata run receiver tracking loop appropriately under demanding "military-spec" speed, acceleration and jerk; Locata demonstrate receiver acquisition and tracking Locata positioning signals in the range of at least 30 miles (50 km), navigation solutions show with tropospheric models, the sufficient large tropospheric error by terrestrial signals in this range; reduce demonstrates a carrier phase "truth-reference solution for the 746TS of the development, production and new stations and aircraft antennae show features provide both satisfactory coverage of WSMR test and reasonable income and multipath mitigation for the aircraft. The new antennas antennas have been developed in collaboration with Cooper Ltd Marlow, Buckinghamshire, United Kingdom.

John Raquet, Director of the advanced navigation technology center at the air force Institute of technology and Chairman of the satellite for the Institute of navigation, the Group joined six other positioning perform experts from the 746TS Australian headquarters of the Locata vx6.0 of a four-day, performed, a careful review and analysis of real data of Locata while two flight studies on a 600-square mile LocataNet provided to Cooma airport in southern New South Wales. Was Locata produced a CDR-final report forgiven and accepted according to this analysis. Locata has now officially pointed out was that the NGBPS-CDR objectives and the CDR is officially closed.

The next step will be deploying Locata of technology in the White Sands Missile range in October 2011. The 746TS to a paper on the NGBPS program on the Institute of navigation (ION)-GNSS 2011-Conference in September in Portland, to present Oregon. The paper is the story of the 746TS positioning functions, and the financial results of relevant Locata flight tests set out.

First Galileo satellite launch in French Guiana for October comes

2011-09-13T13:38:00.000-05:00

GALILEO IOV FM2 lands satellites in French Guiana.

Who has arrived first Galileo navigation satellite in Europe's spaceport in Kourou, Guyana, reports preparations to start start 20 October, the European Space Agency (ESA). Packed in a protective, air-conditioned container, landed the satellite, known as flight model 2 (FM2) in Cayenne-Rochambeau airport on board an Antonov aircraft at local time 06: 45 on Wednesday after the departure from Rome of Thales Alenia Space Italy, where it was built.

A Thales and ESA team stand ready, FM2, having flown in Guyana of last week, together with the entire test and equipment received. The team Space Center loaded the satellite container on a truck for transport of Guyana, where it arrived at 10: 00 local time, and moved in the preparation plant. It remained there over night for the temperature to solve before it was taken the next morning from its container.

FM2 to satellite aboard a vehicle Soyuz ST-B on January 20, along with a second Galileo satellite called the proto flight model (PFM), now prepared for the own flight to Guyana starts are.

This is the first launch of the Russian Soyuz rocket from French Guiana and the first Soyuz launch from a Cosmodrome Baikonur in Kazakhstan or Plesetsk in Russia be. The introduction is a new facility 13 km northwest of the Ariane-5 launch site of the. French Guiana is much closer to the equator, thus each time benefit from the Earth rotate, increase the maximum payload in geostationary orbit of 1.7 tonnes 3 tonnes.

The first four Galileo satellites, built by a consortium led by EADS Astrium Germany, form the operational core of full Galileo Satnav constellation.

See the ESA website.

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Spatial genius and other GIS education

2011-09-13T09:38:00.000-05:00

The education services Australia (ESA) has spatial genius, to promote an educational system of GIS in Australian schools. This function is the first time the education system in Australia has invested in the development and promotion of GIS in schools.

-Asian surveying and mapping

The first day of September marked the top who took College of Sciences, engineering, and Agriculture (CSEA) in A & M-Commerce as a new Dean price Blount the first official day, the Dr. Grady.

And, no, he is not a geographer, but he thinks like a:

The Blount background is particularly in astronomy. He worked with distributed Active Archive Center, the collection of data gateway for NASA's Earth science enterprise. His expertise in this area could help, what he hopes to start the CSEA latest project: Geospatial Intelligence science.

-The East Texan

For those of you in education, but your classes and issues at your University I recommend documentaries from American public media to education. The current series of three hour long programs is called morning College. You focus on the changing state of College teaching and learning, growing interest in certificates, how is not for everyone and how we can get those, who do not finish to do so later. I have never disappointed by any of the edu docs for this group, and I have almost all of them.

-Amerikanische radio work

Tim mullet, University of Alaska Fairbanks graduate student, is sound - natural and artificial - assign in the Kenai national wildlife refuge in Alaska. His recorder capture sound for 20 seconds every 15 minutes, and he has tools to identify the artificial sounds.

Mullet can then drag these data in a GIS system and create a map of exactly where the sounds in the refuge occur. Areas which are marked in red contain high levels of unnatural or mechanical sounds and often with proximity to the development or road to coordinate systems.

Of which she most was, the resulting data - from December to April - several models, he provided to the best interpretation of the refuge be compiled soundscape and Anthrophony, including the snow machines to get.

-Penninsula Clarion

00 from Adena protection mountain on 09 / 06 at 03:

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India uses GIS combat illegal buildings, posters, and other international-GIS-News

2011-09-13T05:38:00.000-05:00

BMC Deputy Commissioner Priyadarshi Mohapatra said, "we are planning, the help of GIS (geographical information system) system to control the Horten management in the city." Mohapatra added: "the images from satellites can help us to monitor ad agencies so that they do not cheat us." Photos by high resolution satellite images generated are in computers to know, the exact size and position from the billboards be included. "After the images are obtained, we can do the data compare physical."

-Times of India

In Thane, the subject is private based on State-owned land. Again, GIS to help!

"Government asks Thane municipal Commissioner in a week to submit a report on these illegal structures, with the help of global information system (GIS) to map out, platform, slum Pocket locations and various other aspects" they

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What NYC learned to Irene and other Government GIS News

2011-09-13T01:38:00.000-05:00

New York City is the "lessons" detailed after the visit of Hurricane Irene. Of course, some concern cards.

Mayor's Office of the traffic on nyc.gov had predicted, for example, an increase, when it issued the evacuation order. But no one expects that five times the normal volume of traffic. Friday afternoon overloaded had become strong computer servers. The website sputtered and crashed for hours when New York's most needed it.

In the future, the city will try to change, so that it quickly can - be stripped a few basics such as an evacuation map website, postal code searchable - are in highest demand during an emergency.

Also there were some problems with evacuation zones, at least, that probably should have extended one of.

-New York Times

It has more than 10 years, but approved by the United States Board on geographic names has removed the final racist insults the last place name changes from Maine cards.

The six locations, all in Aroostook County, are now named Scopan, Scopan Bay, Scopan knob, Scopan Lake, Scopan mountain and Scopan stream.

The old names contain sounds, the reference in the native American dialects, "women and in the evening."

-Bangor Daily News

Developed to online services by IKM for local self-government (LSG) Department of the Karala State is a geographic information system India cadastral maps (gis.lsgkerala.gov.in). There is no disclaimer and data are protected by copyright.

Kerala IT news

43 of Adena protection mountain on 09 / 07 at 05:

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Texas Wildfire Mapping - interactive and non-interactively

2011-09-12T21:38:00.000-05:00

If it is life Houston here, such as the local newspaper you one transformed evacuation order said:

UPDATE: The mandatory evacuation for Montgomery County residents living East of FM 1486 in key card grids 181 M-R-V-Z was abolished.

This area covers shady Oaks Blvd, shady Oaks, shady Lane, country Oaks, Weeren road, N. Hall drive, S. Hall drive, DOMA and Sandy Hill Road.

Montgomery County Office of emergency management posted an interactive map of GIS for the fires in Montgomery County.

Go to the left of the screen on www.mctxoem.org, and click on "GIS map", or visit emergency news and information.

The first bit sounds like here in Boston, but locally, I'm Goobledook sure that it has meaning. FM1486 seems a road. I am pleased that street names were also included. What is very disappointing, that the show no special URL. Why not? Why add an additional step to access the information?

-Your Houston News

Texas forest service builds the flames to fight, and you can check their progress at any time by viewing an interactive map, you can find by clicking here.

-CBS 7

ESRI, well, actually Meltwater press (meltwater press is a Web-based media contact database and distribution, which identified journalists/beats and builds relevant media lists.) sent the list:

This ESRI wildfires map showing fire information in the and to the Central Texas region. It is free to use and reporting can be easily adapted. The Centre of the map change simply zoom or move to an area of interest. Turn off layers or, customize the display. Use the social and the gear icon to change the search tagging and date ranges. Use the share button, to a unique URL to your custom card build after the changes or use the corresponding code on the map to embed on your site. Map showing data from multiple sources, including the USGS NHSS and MODIS global fires. See more cards. If you questions or need assistance please contact.(JavaScript must be enabled to view this email address).

Me I question how many publications vs. connection make their own cards to local authorities cards?

-Meltwater press

In Bastrop, where two deaths by fire related, there is a list of the damaged structures and a map in PDF format.

-KUT

Waller County has a PDF of the evacuation area.

-Houston Chronicle

00 from Adena protection mountain on 09 / 08 at 03:

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Directions news quiz 9 September 2011

2011-09-12T17:38:00.000-05:00

Please enable JavaScript to view the comments powered by Disqus. From direction magazine sponsored podcast: ESRI software helps real estate developers who select the best locations Podcast: a look back at 9 / 11 and GIS in New York - an interview with Al Leidner, New York City GIS Director in 2001 GIS community can look back on 9 / 11 what geo-literacy Coalition to geographical preparation at FOSS4G tackles Americans expect 2011

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Apple patent application: Crowdsourcing data for local search

2011-09-12T13:38:00.000-05:00

The patent application on Thursday by AppleInsider discovered and is titled "Relevance ranking for the search in connection with the card." ""It described", such as an iPhone optionally the location of a user available, to improve your search results via GPS, Apple would help."

Abstract

The following refers to the search ranking results consisting of from sites or recommend to visit places based on stored data, the visits by thousands of users to the sites represented as search results or recommended to visit sites. The data that users visit can be recorded by receiving performed data anonymously sent to the diversity of the user of handheld communication devices. A handheld communication device, which is run by a user, the system can optionally associated with the user's location time stamp report. The handheld communication device can be either a single site-coordinate or a collection of coordinates that collected are reported in the course of time.

He is former Placebaser Jaron Waldman and SR Apple's Director of product marketing, Chad of Richards and the app-is assigned from March 2010

AppleInsider

48 of Adena protection mountain on 09 / 09 to 03:

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Hear Lightsquared update – Congress, company changes plan again - 09.09.11

2011-09-12T09:38:00.000-05:00

Most of the witnesses and some legislators in the Committee calls for additional testing of the LightSquared of the proposal, only the lower band of the spectrum for now, it submitted on 30 June. LightSquared Executive Vice President Jeffrey Carlisle said that about 130 products in this volume in a series of tests have been tested this year.

However, said to try an additional plan to the FCC, a solution for the interference of LightSquared has now submitted Carlisle. In the newspaper Wednesday filed the company proposed, on a certain level the consignment turns its LTE towers, measured on the ground at different distances from each tower is obligated.

The company has also proposed a stable satellite signal offers services for GPS augmentation that high-precision GPS devices, to another part of the LightSquared the band use.

If nothing else seems the pressure in the compromise add this move to grow.

PC world, see also: the Hill

09 of Adena protection mountain on 09 / 09 to 04:

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Indian University and other GIS education help Spanish GIS educator

2011-09-12T05:38:00.000-05:00

Dr. Miguel Calvo Melero, University of the Basque country - Spain, will be providing technical assistance at University in setting up GIS-R & D Center, using a variety of software. He is training students of GIS and spatial data analysis, a field where employment opportunities are plenty.

He a to start five professors from around the world, new programs at the University of India. And Yes, I see also the irony in the concept of "Manifold" here.

Press release

The Department of energy received $2.8 million Center for advanced energy studies to study the suitability of the sites for solar power plants.

The three year project checks the proposed sites for the critical factors to determine their economic and social suitability, such as how much sun, given to them, how close they water and essential proximity are, to electrical transmission facilities.

Boise State University energy policy Institute runs the program. BSU researchers are developing a geographic information system (GIS) project planning tool, to measurable properties and constraints identify plant sites based utility-scale solar will help developers and other interested parties.

-Idaho Statesman

I love that the University of Wyoming is a geographic information science center (WyGISC) OpenStreetMap mapping party of 1-19 Saturday, is Sept. 17 hosted. Bad: "the mapping event is free and open to people 18 years and older". Me I question, why? School policy?

Press release

19 by Adena protection mountain on 09 / 09 to 04:

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The Early Days of GPS

2009-05-20T14:10:00.001-05:00

THE EARLY DAYS OF GPS

Like the Internet, which arose from a 1969 research project of the U.S. Defense Department, GPS began as a military research project in the 1960s and 1970s. The idea was to fly atomic clocks on satellites and use the data for navigation.

The system has several components: a constellation of 24 NAVSTAR satellites (operated by the U.S. Air Force) in Earth orbit with atomic clocks aboard, ground stations that control the system, five on-orbit spare satellites and receivers for users.

GPS satellite launches started in 1978, and second-generation satellites were launched beginning in 1989. The system became fully operational in 1995, with a signal for military users and a less-accurate signal for civilians, but the commercial market had begun to open up more than a decade earlier.

In 1983, Soviet jet interceptors shot down a Korean Air civilian airliner carrying 269 passengers that had mistakenly entered Soviet airspace.

Because crew access to better navigational tools might have prevented the disaster, President Ronald Reagan issued a directive guaranteeing that GPS signals would be available at no charge to the world when the system became operational. The commercial market has grown steadily ever since.

In 2004, President Bush issued an updated policy that keeps civilian GPS free of direct user fees.

Navstar

2009-05-15T21:16:00.001-05:00

Originally designated the NAVSTAR (Navigation System with Timing And Ranging) Global Positioning System, GPS was developed by the US Department of Defense to provide all-weather round-the-clock navigation capabilities for military ground, sea, and air forces. Since its implementation, GPS has also become an integral asset in numerous civilian applications and industries around the globe, including recreational uses (e.g. boating, aircraft, hiking), corporate vehicle fleet tracking, and surveying.

GPS employs 24 spacecraft in 20,200 km circular orbits inclined at 55 degrees. These spacecraft are placed in 6 orbit planes with four operational satellites in each plane. All launches have been successful except for one launch failure in 1981. The full 24-satellite constellation was completed on March 9, 1994.

GPS receivers use triangulation of the GPS satellites' navigational signals to determine their location. The satellites provide two different signals that provide different accuracies. Coarse-acquisition (C/A) code is intended for civilian use, and is deliberately degraded. The accuracy using a typical civilian GPS receiver with C/A code is typically about 100 meters. The military's Precision (P) code is not corrupted, and provides positional accuracy to within approximately 20 meters. Numerous on-line tutorials on how GPS works and its applications are available, including those at the Univ. of Texas and Rentec International. GPS satellites are controlled at the GPS Master Control Station (MCS) located at Falcon Air Force Base outside Colorado Springs, Colorado. The ground segment also includes four active-tracking ground antennas and five passive-tracking monitor stations.

GPS Myths

2009-05-14T06:31:00.000-05:00

This document is designed to dispel GPS collection myths and give sound advice for digitizing with GPS receivers intended for GIS.

Myth: My recreational grade GPS always gets data when my expensive receiver does not. Is it worth to keep this expensive rock around any longer?

Reality: GPS units vary in the ability to see GPS signals and allow a position to be collected. Usually, for GIS data collection purposes (at least in the NPS), the horizontal position needs to be within a couple of meters from the true location. More expensive mapping/resource grade receivers can be set to automatically filter out poorer quality positions. Recreational grade receivers will allow a position to be collected at any level of horizontal positional accuracy and do not store any estimates of error.

Myth: The GPS unit is the most important item to purchase. Software is secondary.

Reality: Not anymore. With Windows CE-based dataloggers the choices of mix/matching the GPS receiver, the datalogger, CE-based GPS software and PC software must be considered before deciding on a “GPS unit”. A GPS unit may be cheap, but after you add the software, training and cabling to get a “system” to work you may equal the amount of money on a more expensive GPS system that pre-plans, structures the attribute collection, collects and filters the GPS data and post-processes for the GIS. Don’t get caught up in going cheap, since the real work begins AFTER you have collected the GPS data. Some GPS solutions leave you with limited means to pass into the corporate GIS, high quality data and accuracy statements for documentation.

Myth: Now that I purchased a receiver with WAAS, I don’t need to augment GPS positions with realtime DGPS equipment or post-processing.

Reality: Relying on WAAS for 100% of your DGPS needs is not realistic. WAAS is designed by the FAA to guide aircraft down to 200’ above the surface of the earth. WAAS differential will not work effectively under tree canopy and when the southern sky is occluded. Relying on WAAS for your DGPS needs will introduce data into your corporate datasets that may be more accurate sometimes and not so accurate other times. How will you know? A better solution is investing in real-time differential systems or those systems that utilize post-processing differential. Using equipment that post-processes ensures 100% differential processing for your GIS needs.

Myth: All I need is the GPS receiver and no external antenna.

Reality: The key to receiving high quality GPS data is a clear view of the sky and an un-interrupted strong signal from at least 4 satellites in a good geometric pattern overhead at any one time. Since many mapping missions may be in hilly or mountainous regions, under tree canopy or from within a moving vehicle, holding a GPS unit in your hands can block crucial access to satellites. An external GPS antenna placed above a mapper’s head will maximize the greatest number of satellites to be used in a GPS solution, and often times increase your efficiency in poor GPS environments. An external antenna also allows you to free up your hands to write things down or place the GPS receiver in a storage location (like a pocket) during long stretches of monotonous terrain. We encourage buyers to research the accuracy differences between their GPS receiver’s internal and external antenna and buy the best one available.

Myth: With GPS accuracy getting better and better, there is no reason to average a point location. Just collect an instantaneous position and move on.

Reality: Averaging more than one GPS position while standing still will generate a more accurate position due to simple math. GPS errors are still present and fluctuate; averaging these multiple positions provides a more accurate point.

Purchase GPS units that Average: The following Garmin GPS receivers allow averaging (Garmin III+, 12XL, Map76, 60C). The eTrex series cannot average. All Trimble receivers average positions by default.

Log enough positions. Be sure to log at least 180 positions (For Garmin receivers, that’s 3 minutes at 1 position per second.)

Stand still, but wiggle! This may sound silly, but when averaging a position, you must be not moving. However, in poor GPS environments, like a dense forest, a small movement of the antenna may provide you a position that a few seconds ago was not possible. These subtle antenna movements can provide the crucial signal that allows a position when other GPS quality filters (like PDOP/HDOP, SNR, Elevation Mask) are set appropriately for the situation.

Myth: I simply don’t trust storing my GPS locations on the GPS. I write all my locations down and transfer them into GIS when I get back to the office. I think this is the best route:

Reality: This is a bad idea. Not electronically storing a GPS position places one in the situation where datum’s, coordinate formats and accuracy can all be dropped or confused when entering into a GIS. User error now vastly exceeds GPS error especially since electronic storage of GPS data in receivers is tightly controlled in certain coordinate formats, significant digits and datums allowing for the best position possible. Once the data is stored internally in the GPS, the appropriate software used back in the office will ensure that the data is transferred in the highest quality possible. Contact your park’s GIS coordinator to find out what software should be used to download the GPS. If you must write down a coordinate, then you must write down the datum chosen on the GPS screen display, units and estimated error during collection.

Myth: I don’t need to worry about coordinate systems and datums when using ArcPad.

Reality: Three questions must be ascertained about coordinate systems and datums before you invest in an ArcPad solution for your GIS needs. Not asking these questions first will cause considerable heartache, pain and errors when merging ArcPad data back into your GIS.

Question 1: What is the datum of your GIS Layers?

You should have PRJ (Projection) file assigned for all your GIS layers BEFORE using ArcPAD and they must be all in the same projection. This is because ArcPad “listens” to the PRJ file to assign how to transform GPS input on-the-fly into a shapefile. If you add a layer with no projection (.prj file) to a map with a geographic projection, ArcPad checks if the data appears to be lat-long (geographic) and will assign those data a datum from the apDatums.dbf file. If multiple datums exist with the same name (there are 21 variants of NAD27), then you must use the Select Default Datum tool in the Layers dialog box to select the datum you want. Incorrectly defining the layer’s datum in the field can cause transform errors in relation to the GIS layers back in the office. Be very careful and ensure you use ArcGIS to change the projection of your data BEFORE adding it to your ArcPad map.

Question 2: What is the datum of your incoming GPS positions from the GPS receiver?

ArcPad has no control over incoming GPS data, but relies on GPS manufacturer protocols to send data in certain formats and datums. Garmin receivers set to NMEA protocol are dependent on the screen display of the datum. Altering the datum on the Garmin can alter the GPS input so that ArcPad receives data in the wrongly assumed datum! Always set any Garmin in NMEA protocol to WGS84 Datum and never change!. You do not need to worry about TSIP protocol receivers (Trimble), or PLGR’s since GPS input is always WGS84.

Question 3: Are your GIS layers in NAD27?

If so, you should not be using ArcPad for high resolution mapping. Since ArcPad cannot use NADCON, a high quality Datum transform engine, considerable error may result in your GPS positions (1–15 meters). In order to fully utilize GPS technology for your high resolution GIS mapping needs, you should transform all your Park data to NAD83 as soon as possible. Not only will this remove datum transform errors inherent in the older spheroid/datum based coordinate systems, but ensure that your GIS is in the best position possible to receive data from the most incredible digitizing tool we have—GLOBAL POSTIONING SYSTEMS.

How GPS Works

2009-05-13T08:36:00.002-05:00

Trying to figure out where you are and where you're going is probably one of man's oldest pastimes.

Navigation and positioning are crucial to so many activities and yet the process has always been quite cumbersome.

Over the years all kinds of technologies have tried to simplify the task but every one has had some disadvantage.

Landmarks: Only work in local area. Subject to movement or destruction by environmental factors.

Dead Reckoning: Very complicated. Accuracy depends on measurement tools which are usually relatively crude. Errors accumulate quickly.

Celestial: Complicated. Only works at night in good weather. Limited precision.

OMEGA: Based on relatively few radio direction beacons. Accuracy limited and subject to radio interference.

LORAN: Limited coverage (mostly coastal). Accuracy variable, affected by geographic situation. Easy to jam or disturb.

SatNav: Based on low-frequency doppler measurements so it's sensitive to small movements at receiver. Few satellites so updates are infrequent.

Finally, the U.S. Department of Defense decided that the military had to have a super precise form of worldwide positioning. And fortunately they had the kind of money ($12 billion!) it took to build something really good.

Why did the Department of Defense develop GPS?
In the latter days of the arms race the targeting of ICBMs became such a fine art that they could be expected to land right on an enemy's missile silos. Such a direct hit would destroy the silo and any missile in it. The ability to take out your opponent's missiles had a profound effect on the balance of power.
But you could only expect to hit a silo if you knew exactly where you were launching from. That's not hard if your missiles are on land, as most of them were in the Soviet Union. But most of the U.S. nuclear arsenal was at sea on subs. To maintain the balance of power the U.S. had to come up with a way to allow those subs to surface and fix their exact position in a matter of minutes anywhere in the world......Hello GPS!

The result is the Global Positioning System, a system that's changed navigation forever. The Global Positioning System (GPS) is a worldwide radio-navigation system formed from a constellation of 24 satellites and their ground stations.
GPS uses these "man-made stars" as reference points to calculate positions accurate to a matter of meters. In fact, with advanced forms of GPS you can make measurements to better than a centimeter!

Here's how GPS works in five logical steps:
1. The basis of GPS is "triangulation" from satellites.
2. To "triangulate," a GPS receiver measures distance using the travel time of radio signals.
3. To measure travel time, GPS needs very accurate timing which it achieves with some tricks.
4. Along with distance, you need to know exactly where the satellites are in space. High orbits and careful monitoring are the secret.
5. Finally you must correct for any delays the signal experiences as it travels through the atmosphere.

Improbable as it may seem, the whole idea behind GPS is to use satellites in space as reference points for locations here on earth.
That's right, by very, very accurately measuring our distance from three satellites we can " triangulate " our position anywhere on earth.
Forget for a moment how our receiver measures this distance. We'll get to that later.

First consider how distance measurements from three satellites can pinpoint you in space.

The Big Idea Geometrically:
Suppose we measure our distance from a satellite and find it to be 11,000 miles.
Knowing that we're 11,000 miles from a particular satellite narrows down all the possible locations we could be in the whole universe to the surface of a sphere that is centered on this satellite and has a radius of 11,000 miles.
Next, say we measure our distance to a second satellite and find out that it's 12,000 miles away.
That tells us that we're not only on the first sphere but we're also on a sphere that's 12,000 miles from the second satellite. Or in other words, we're somewhere on the circle where these two spheres intersect.
If we then make a measurement from a third satellite and find that we're 13,000 miles from that one, that narrows our position down even further, to the two points where the 13,000 mile sphere cuts through the circle that's the intersection of the first two spheres.
So by ranging from three satellites we can narrow our position to just two points in space.
To decide which one is our true location we could make a fourth measurement. But usually one of the two points is a ridiculous answer (either too far from Earth or moving at an impossible velocity) and can be rejected without a measurement.
A fourth measurement does come in very handy for another reason however, but we'll tell you about that later.
Next we'll see how the system measures distances to satellites.
But how can you measure the distance to something that's floating around in space? We do it by timing how long it takes for a signal sent from the satellite to arrive at our receiver.

The Big Idea Mathematically
In a sense, the whole thing boils down to those “velocity times travel time” math problems we did in high school. Remember the old: “If a car goes 60 miles per hour for two hours, how far does it travel?”
Velocity (60 mph) x Time (2 hours) = Distance (120 miles)
In the case of GPS we're measuring a radio signal so the velocity is going to be the speed of light or roughly 186,000 miles per second.
The problem is measuring the travel time.
The timing problem is tricky. First, the times are going to be awfully short. If a satellite were right overhead the travel time would be something like 0.06 seconds. So we're going to need some really precise clocks. We'll talk about those soon.
But assuming we have precise clocks, how do we measure travel time? To explain it let's use a goofy analogy:
Suppose there was a way to get both the satellite and the receiver to start playing "The Star Spangled Banner" at precisely 12 noon. If sound could reach us from space (which, of course, is ridiculous) then standing at the receiver we'd hear two versions of the Star Spangled Banner, one from our receiver and one from the satellite.
These two versions would be out of sync. The version coming from the satellite would be a little delayed because it had to travel more than 11,000 miles.
If we wanted to see just how delayed the satellite's version was, we could start delaying the receiver's version until they fell into perfect sync.
The amount we have to shift back the receiver's version is equal to the travel time of the satellite's version. So we just multiply that time times the speed of light and BINGO! we've got our distance to the satellite.
That's basically how GPS works.

Only instead of the Star Spangled Banner the satellites and receivers use something called a "Pseudo Random Code" - which is probably easier to sing than the Star Spangled Banner.
The Pseudo Random Code (PRC, shown above) is a fundamental part of GPS. Physically it's just a very complicated digital code, or in other words, a complicated sequence of "on" and "off" pulses as shown here:
The signal is so complicated that it almost looks like random electrical noise. Hence the name "Pseudo-Random."
{GPS Signals in detail
Carriers
The GPS satellites transmit signals on two carrier frequencies. The L1 carrier is 1575.42 MHz and carries both the status message and a pseudo-random code for timing.
The L2 carrier is 1227.60 MHz and is used for the more precise military pseudo-random code.

Pseudo-Random Codes
There are two types of pseudo-random code (see tutorial for explanation of pseudo random codes in general). The first pseudo-random code is called the C/A (Coarse Acquisition) code. It modulates the L1 carrier. It repeats every 1023 bits and modulates at a 1MHz rate. Each satellite has a unique pseudo-random code. The C/A code is the basis for civilian GPS use.
The second pseudo-random code is called the P (Precise) code. It repeats on a seven day cycle and modulates both the L1 and L2 carriers at a 10MHz rate. This code is intended for military users and can be encrypted. When it's encrypted it's called "Y" code. Since P code is more complicated than C/A it's more difficult for receivers to acquire. That's why many military receivers start by acquiring the C/A code first and then move on to P code.
Navigation Message
There is a low frequency signal added to the L1 codes that gives information about the satellite's orbits, their clock corrections and other system status.}

There are several good reasons for that complexity: First, the complex pattern helps make sure that the receiver doesn't accidentally sync up to some other signal. The patterns are so complex that it's highly unlikely that a stray signal will have exactly the same shape.
Since each satellite has its own unique Pseudo-Random Code this complexity also guarantees that the receiver won't accidentally pick up another satellite's signal. So all the satellites can use the same frequency without jamming each other. And it makes it more difficult for a hostile force to jam the system. In fact the Pseudo Random Code gives the DoD a way to control access to the system.
{Encrypted GPS
GPS was developed by the Defense Department primarily for military purposes. And even though it's been estimated that there are ten times as many civilian receivers as military ones the system still has considerable military significance.
To that end the military maintains exclusive access to the more accurate "P-code" pseudo random code. It's ten times the frequency of the civilian C/A code (and so potentially much more accurate) and much harder to jam. When it's encrypted it's called "Y-code" and only military receivers with the encryption key can receive it. Because this code is modulated on two carriers, sophisticated games can be played with the frequencies to help eliminate errors caused by the atmosphere.}

But there's another reason for the complexity of the Pseudo Random Code, a reason that's crucial to making GPS economical. The codes make it possible to use "information theory" to " amplify " the GPS signal. And that's why GPS receivers don't need big satellite dishes to receive the GPS signals.

Expanded Topic:
Using the Pseudo Random Code as an amplifier.
The pseudo random code is one of the brilliant ideas behind GPS. It not only acts as a great timing signal but it also gives us a way to "amplify" the very weak satellite signals.
Here's how that amplification process works:
The world is awash in random electrical noise. If we tuned our receivers to the GPS frequency and graphed what we picked up, we'd just see a randomly varying line --- the earth's background noise. The GPS signal would be buried in that noise.

The pseudo random code looks a lot like the background noise but with one important difference: we know the pattern of its fluctuations.
What if we compare a section of our PRC with the background noise and look for areas where they're both doing the same thing?
We can divide the signal up into time periods (called "chipping the signal") and then mark all the periods where they match (i.e. where the background is high when the PRC is high).

Since both signals are basically random patterns, probability says that about half the time they'll match and half the time they won't.
If we set up a scoring system and give ourselves a point when they match and take away a point when they don't, over the long run we'll end up with a score of zero because the -1's will cancel out the 1's.
But now if a GPS satellite starts transmitting pulses in the same pattern as our pseudo random code, those signals, even though they're weak, will tend to boost the random background noise in the same pattern we're using for our comparison.
Background signals that were right on the border of being a "1" will get boosted over the border and we'll start to see more matches. And our "score" will start to go up.

Even if that tiny boost only puts one in a hundred background pulses over the line, we can make our score as high as we want by comparing over a longer time. If we use the 1 in 100 figure, we could run our score up to ten by comparing over a thousand time periods.
If we compared the PRC to pure random noise over a thousand time periods our score would still be zero, so this represents a ten times amplification.
This explanation is a greatly simplified but the basic concept is significant. It means that the system can get away with less powerful satellites and our receivers don't need big antennas like satellite TV.
You may wonder why satellite TV doesn't use the same concept and eliminate those big dishes. The reason is speed.
The GPS signal has very little information in it. It's basically just a timing pulse, so we can afford to compare the signal over many time periods. A TV signal carries a lot of information and changes rapidly. The comparison system would be too slow and cumbersome.

We glossed over one point in our goofy Star-Spangled Banner analogy. It assumes that we can guarantee that both the satellite and the receiver start generating their codes at exactly the same time. But how do we make sure everybody is perfectly synced? Stay tuned and see.

In Review: Measuring Distance
1. Distance to a satellite is determined by measuring how long a radio signal takes to reach us from that satellite.
2. To make the measurement we assume that both the satellite and our receiver are generating the same pseudo-random codes at exactly the same time.
3. By comparing how late the satellite's pseudo-random code appears compared to our receiver's code, we determine how long it took to reach us.
4. Multiply that travel time by the speed of light and you've got distance
If measuring the travel time of a radio signal is the key to GPS, then our stop watches had better be darn good, because if their timing is off by just a thousandth of a second, at the speed of light, that translates into almost 200 miles of error!
On the satellite side, timing is almost perfect because they have incredibly precise atomic clocks on board.
Atomic Clocks
Atomic clocks don't run on atomic energy. They get the name because they use the oscillations of a particular atom as their "metronome." This form of timing is the most stable and accurate reference man has ever developed.

But what about our receivers here on the ground?
Remember that both the satellite and the receiver need to be able to precisely synchronize their pseudo-random codes to make the system work.
If our receivers needed atomic clocks (which cost upwards of $50K to $100K) GPS would be a lame duck technology. Nobody could afford it.
Luckily the designers of GPS came up with a brilliant little trick that lets us get by with much less accurate clocks in our receivers. This trick is one of the key elements of GPS and as an added side benefit it means that every GPS receiver is essentially an atomic-accuracy clock.
{Using GPS for Timing
We generally think of GPS as a navigation or positioning resource but the fact that every GPS receiver is synchronized to universal time makes it the most widely available source of precise time.
This opens up a wide range of applications beyond positioning. GPS is being used to synchronize computer networks, calibrate other navigation systems, synchronize motion picture equipment and much more.}
The secret to perfect timing is to make an extra satellite measurement.
That's right, if three perfect measurements can locate a point in 3-dimensional space, then four imperfect measurements can do the same thing.
Extra Measurement Cures Timing Offset
If our receiver's clocks were perfect, then all our satellite ranges would intersect at a single point (which is our position). But with imperfect clocks, a fourth measurement, done as a cross-check, will NOT intersect with the first three.
So the receiver's computer says "Uh-oh! there is a discrepancy in my measurements. I must not be perfectly synced with universal time."
Since any offset from universal time will affect all of our measurements, the receiver looks for a single correction factor that it can subtract from all its timing measurements that would cause them all to intersect at a single point.
That correction brings the receiver's clock back into sync with universal time, and bingo! - you've got atomic accuracy time right in the palm of your hand.
Once it has that correction it applies to all the rest of its measurements and now we've got precise positioning.
One consequence of this principle is that any decent GPS receiver will need to have at least four channels so that it can make the four measurements simultaneously.
With the pseudo-random code as a rock solid timing sync pulse, and this extra measurement trick to get us perfectly synced to universal time, we have got everything we need to measure our distance to a satellite in space.
But for the triangulation to work we not only need to know distance, we also need to know exactly where the satellites are.

In Review: Getting Perfect Timing
1. Accurate timing is the key to measuring distance to satellites.
2. Satellites are accurate because they have atomic clocks on board.
3. Receiver clocks don't have to be too accurate because an extra satellite range measurement can remove errors.
In this tutorial we've been assuming that we know where the GPS satellites are so we can use them as reference points.
But how do we know exactly where they are? After all they're floating around 11,000 miles up in space.
A high satellite gathers no moss
That 11,000 mile altitude is actually a benefit in this case, because something that high is well clear of the atmosphere. And that means it will orbit according to very simple mathematics.
The Air Force has injected each GPS satellite into a very precise orbit, according to the GPS master plan.
{GPS Master Plan
The launch of the 24th block II satellite in March of 1994 completed the GPS constellation.
Four additional satellites are in reserve to be launched "on need."
The spacings of the satellites are arranged so that a minimum of five satellites are in view from every point on the globe. }
On the ground all GPS receivers have an almanac programmed into their computers that tells them where in the sky each satellite is, moment by moment.
The basic orbits are quite exact but just to make things perfect the GPS satellites are constantly monitored by the Department of Defense. {These stations monitor the GPS satellites, checking both their operational health and their exact position in space. The master ground station transmits corrections for the satellite's ephemeris constants and clock offsets back to the satellites themselves. The satellites can then incorporate these updates in the signals they send to GPS receivers.
There are five monitor stations: Hawaii, Ascension Island, Diego Garcia, Kwajalein, and Colorado Springs. }
They use very precise radar to check each satellite's exact altitude, position and speed.
The errors they're checking for are called "ephemeris errors" because they affect the satellite's orbit or "ephemeris." These errors are caused by gravitational pulls from the moon and sun and by the pressure of solar radiation on the satellites.
The errors are usually very slight but if you want great accuracy they must be taken into account.
Getting the message out
Once the DoD has measured a satellite's exact position, they relay that information back up to the satellite itself. The satellite then includes this new corrected position information in the timing signals it's broadcasting.
So a GPS signal is more than just pseudo-random code for timing purposes. It also contains a navigation message with ephemeris information as well.
With perfect timing and the satellite's exact position you'd think we'd be ready to make perfect position calculations. But there's trouble afoot. Check out the next section to see what's up.

In Review: Satellite Positions
1. To use the satellites as references for range measurements we need to know exactly where they are.
2. GPS satellites are so high up their orbits are very predictable.
3. Minor variations in their orbits are measured by the Department of Defense.
4. The error information is sent to the satellites, to be transmitted along with the timing signals.
Up to now we've been treating the calculations that go into GPS very abstractly, as if the whole thing were happening in a vacuum. But in the real world there are lots of things that can happen to a GPS signal that will make its life less than mathematically perfect.
To get the most out of the system, a good GPS receiver needs to take a wide variety of possible errors into account. Here's what they've got to deal with.
First, one of the basic assumptions we've been using throughout this tutorial is not exactly true. We've been saying that you calculate distance to a satellite by multiplying a signal's travel time by the speed of light. But the speed of light is only constant in a vacuum.
As a GPS signal passes through the charged particles of the ionosphere and then through the water vapor in the troposphere it gets slowed down a bit, and this creates the same kind of error as bad clocks.
There are a couple of ways to minimize this kind of error. For one thing we can predict what a typical delay might be on a typical day. This is called modeling and it helps but, of course, atmospheric conditions are rarely exactly typical.
{Error Modeling
Much of the delay caused by a signal's trip through our atmosphere can be predicted.
Mathematical models of the atmosphere take into account the charged particles in the ionosphere and the varying gaseous content of the troposphere.
On top of that, the satellites constantly transmit updates to the basic ionospheric model.
A GPS receiver must factor in the angle each signal is taking as it enters the atmosphere because that angle determines the length of the trip through the perturbing medium.}

Another way to get a handle on these atmosphere-induced errors is to compare the relative speeds of two different signals. This " dual frequency" measurement is very sophisticated and is only possible with advanced receivers.
{Dual Frequency Measurements
Physics says that as light moves through a given medium, low-frequency signals get "refracted" or slowed more than high-frequency signals.
By comparing the delays of the two different carrier frequencies of the GPS signal, L1 and L2, we can deduce what the medium (i.e. atmosphere) is, and we can correct for it.
Unfortunately this requires a very sophisticated receiver since only the military has access to the signals on the L2 carrier.
Civilian companies have worked around this problem with some tricky strategies.
Unfortunately they're so secret if we told you how they work we'd have to kill you. }
Trouble for the GPS signal doesn't end when it gets down to the ground. The signal may bounce off various local obstructions before it gets to our receiver.
This is called multipath error and is similar to the ghosting you might see on a TV. Good receivers use sophisticated signal rejection techniques to minimize this problem.
{Multipath error
The whole concept of GPS relies on the idea that a GPS signal flies straight from the satellite to the receiver.
Unfortunately, in the real world the signal will also bounce around on just about everything in the local environment and get to the receiver that way too.
The result is a barrage of signals arriving at the receiver: first the direct one, then a bunch of delayed reflected ones. This creates a messy signal.
If the bounced signals are strong enough they can confuse the receiver and cause erroneous measurements.
Sophisticated receivers use a variety of signal processing tricks to make sure that they only consider the earliest arriving signals (which are the direct ones).}
Problems at the satellite
Even though the satellites are very sophisticated they do account for some tiny errors in the system.
The atomic clocks they use are very, very precise but they're not perfect. Minute discrepancies can occur, and these translate into travel time measurement errors.
And even though the satellites positions are constantly monitored, they can't be watched every second. So slight position or " ephemeris" errors can sneak in between monitoring times.

{Ephemeris errors
Ephemeris (or orbital) data is constantly being transmitted by the satellites.
Receivers maintain an "almanac" of this data for all satellites and they update these almanacs as new data comes in.
Typically, ephemeris data is updated hourly. }
Basic geometry itself can magnify these other errors with a principle called "Geometric Dilution of Precision" or GDOP.
It sounds complicated but the principle is quite simple.
There are usually more satellites available than a receiver needs to fix a position, so the receiver picks a few and ignores the rest.
If it picks satellites that are close together in the sky the intersecting circles that define a position will cross at very shallow angles. That increases the gray area or error margin around a position.
If it picks satellites that are widely separated the circles intersect at almost right angles and that minimizes the error region.
Good receivers determine which satellites will give the lowest GDOP.
Intentional Errors!
As hard as it may be to believe, the same government that spent $12 billion to develop the most accurate navigation system in the world intentionally degraded its accuracy. The policy was called "Selective Availability" or "SA" and the idea behind it was to make sure that no hostile force or terrorist group can use GPS to make accurate weapons.

Basically the DoD introduced some "noise" into the satellite's clock data which, in turn, added noise (or inaccuracy) into position calculations. The DoD may have also been sending slightly erroneous orbital data to the satellites which they transmitted back to receivers on the ground as part of a status message.

Together these factors made SA the biggest single source of inaccuracy in the system. Military receivers used a decryption key to remove the SA errors and so they're much more accurate.

Turning Off Selective Availability

On May 1, 2000 the White House announced a decision to discontinue the intentional degradation of the GPS signals to the public beginning at midnight. Civilian users of GPS are now able to pinpoint locations up to ten times more accurately. As part of the 1996 Presidential Decision Directive goals for GPS, President Clinton committed to discontinuing the use of SA by 2006. The announcement came six years ahead of schedule. The decision to discontinue SA was the latest measure in an on-going effort to make GPS more responsive to civil and commercial users worldwide.

The bottom line

Fortunately all of these inaccuracies still don't add up to much of an error. And a form of GPS called "Differential GPS" can significantly reduce these problems. We'll cover this type of GPS later.

To get an idea of the impact of these errors see a typical error budget:
Summary of GPS Error Sources
Typical Error in Meters (per satellite)
Standard GPS Differential GPS
Satellite Clocks 1.5 0
Orbit Errors 2.5 0
Ionosphere 5.0 0.4
Troposphere 0.5 0.2
Receiver Noise 0.3 0.3
Multipath 0.6 0.6
SA 30 0

Typical Position Accuracy
Horizontal 50 1.3
Vertical 78 2.0
3-D 93 2.8

In Review: Correcting Errors
1. The earth's ionosphere and atmosphere cause delays in the GPS signal that translate into position errors.
2. Some errors can be factored out using mathematics and modeling.
3. The configuration of the satellites in the sky can magnify other errors.
4. Differential GPS can eliminate almost all error.
Why We Need Differential GPS:
Basic GPS is the most accurate radio-based navigation system ever developed. And for many applications it's plenty accurate. But it's human nature to want MORE!
So some crafty engineers came up with "Differential GPS," a way to correct the various inaccuracies in the GPS system, pushing its accuracy even farther.
Differential GPS or "DGPS" can yield measurements good to a couple of meters in moving applications and even better in stationary situations.
That improved accuracy has a profound effect on the importance of GPS as a resource. With it, GPS becomes more than just a system for navigating boats and planes around the world. It becomes a universal measurement system capable of positioning things on a very precise scale.
Differential GPS involves the cooperation of two receivers, one that's stationary and another that's roving around making position measurements.
The stationary receiver is the key. It ties all the satellite measurements into a solid local reference.
Here's how it works:
The problem
Remember that GPS receivers use timing signals from at least four satellites to establish a position. Each of those timing signals is going to have some error or delay depending on what sort of perils have befallen it on its trip down to us.
Since each of the timing signals that go into a position calculation has some error, that calculation is going to be a compounding of those errors.
An extenuating circumstance
Luckily the sheer scale of the GPS system comes to our rescue. The satellites are so far out in space that the little distances we travel here on earth are insignificant.
So if two receivers are fairly close to each other, say within a few hundred kilometers, the signals that reach both of them will have traveled through virtually the same slice of atmosphere, and so will have virtually the same errors
That's the idea behind differential GPS: We have one receiver measure the timing errors and then provide correction information to the other receivers that are roving around. That way virtually all errors can be eliminated from the system, even the pesky Selective Availability error that the DoD puts in on purpose.
The idea is simple. Put the reference receiver on a point that's been very accurately surveyed and keep it there.
This reference station receives the same GPS signals as the roving receiver but instead of working like a normal GPS receiver it attacks the equations backwards.
Instead of using timing signals to calculate its position, it uses its known position to calculate timing. It figures out what the travel time of the GPS signals should be, and compares it with what they actually are. The difference is an "error correction" factor.
The receiver then transmits this error information to the roving receiver so it can use it to correct its measurements.
Since the reference receiver has no way of knowing which of the many available satellites a roving receiver might be using to calculate its position, the reference receiver quickly runs through all the visible satellites and computes each of their errors.
Then it encodes this information into a standard format and transmits it to the roving receivers.
It's as if the reference receiver is saying: "OK everybody, right now the signal from satellite #1 is ten nanoseconds delayed, satellite #2 is three nanoseconds delayed, satellite #3 is sixteen nanoseconds delayed...." and so on.
The roving receivers get the complete list of errors and apply the corrections for the particular satellites they're using.
In the early days of GPS, reference stations were established by private companies who had big projects demanding high accuracy - groups like surveyors or oil drilling operations. And that is still a very common approach. You buy a reference receiver and set up a communication link with your roving receivers.
But now there are enough public agencies transmitting corrections that you might be able to get them for free!
The United States Coast Guard and other international agencies are establishing reference stations all over the place, especially around popular harbors and waterways.
These stations often transmit on the radio beacons that are already in place for radio direction finding (usually in the 300kHz range).
Anyone in the area can receive these corrections and radically improve the accuracy of their GPS measurements. Most ships already have radios capable of tuning the direction finding beacons, so adding DGPS will be quite easy.
Many new GPS receivers are being designed to accept corrections, and some are even equipped with built-in radio receivers.
Post Processing DGPS
Not all DGPS applications are created equal. Some don't need the radio link because they don't need precise positioning immediately.
It's one thing if you're trying to position a drill bit over a particular spot on the ocean floor from a pitching boat, but quite another if you just want to record the track of a new road for inclusion on a map.
For applications like the later, the roving receiver just needs to record all of its measured positions and the exact time it made each measurement.
Then later, this data can be merged with corrections recorded at a reference receiver for a final clean-up of the data. So you don't need the radio link that you have to have in real-time systems.
If you don't have a reference receiver there may be alternative source for corrections in your area. Some academic institutions are experimenting with the Internet as a way of distributing corrections.
There's another permutation of DGPS, called "inverted DGPS," that can save money in certain tracking applications.
Let's say you've got a fleet of buses and you'd like to pinpoint them on street maps with very high accuracy (maybe so you can see which side of an intersection they're parked on or whatever).
Anyway, you'd like this accuracy but you don't want to buy expensive "differential-ready" receivers for every bus.
With an inverted DGPS system the buses would be equipped with standard GPS receivers and a transmitter and would transmit their standard GPS positions back to the tracking office. Then at the tracking office the corrections would be applied to the received positions.
It requires a computer to do the calculations, a transmitter to transmit the data but it gives you a fleet of very accurate positions for the cost of one reference station, a computer and a lot of standard GPS receivers. Such a deal!
If you want to know where DGPS might be headed, take a look at your hand, because soon DGPS may be able to resolve positions that are no farther apart than the width of your little finger.
Imagine the possibilities. Automatic construction equipment could translate CAD drawings into finished roads without any manual measurements. Self-guided cars could take you across town while you quietly read in the back seat.
To understand how this kind of GPS is being developed you need to understand a little about GPS signals. If two receivers are fairly close to each other, say within a few hundred kilometers, the signals that reach both of them will have traveled through virtually the same slice of atmosphere, and so will have virtually the same line.
The words "Code-Phase" and "Carrier-Phase" may sound like electronic mumbo-jumbo but, in fact, they just refer to the particular signal that we use for timing measurements. Using the GPS carrier frequency can significantly improve the accuracy of GPS.
The concept is simple but to understand it let's review a few basic principles of GPS.
Remember that a GPS receiver determines the travel time of a signal from a satellite by comparing the "pseudo random code" it's generating, with an identical code in the signal from the satellite.
The receiver slides its code later and later in time until it syncs up with the satellite's code. The amount it has to slide the code is equal to the signal's travel time.
The problem is that the bits (or cycles) of the pseudo random code are so wide that even if you do get synced up there's still plenty of slop.
Consider these two signals:
If you compared them logically you'd say they matched. When signal A is a one, signal B is a one. When signal A is a zero, signal B is a zero.
But you can see that while they match they're a little out of phase. Notice that signal A is a signals would still match logically.
That's the problem with code-phase GPS. It's comparing pseudo random codes that have a cycle width of almost a microsecond. And at the speed of light a microsecond is almost 300 meters of error!
Code-phase GPS isn't really that bad because receiver designers have come up with ways to make sure that the signals are almost perfectly in phase. Good machines get with in a percent or two. But that's still at least 3-6 meters of error.
Survey receivers beat the system by starting with the pseudo random code and then move on to measurements based on the carrier frequency for that code. This carrier frequency is much higher so its pulses are much closer together and therefore more accurate.
If you're rusty on the subject of carrier frequencies consider your car radio. When you tune to 94.7 on the dial you're locking on to a carrier frequency that's 94.7 MHz.
Obviously we can't hear sounds at 94 million cycles a second. The music we hear is a modulation (or change) in this carrier frequency. So when you hear someone sing an "A" note on the radio you're actually hearing the 94.7 MHz carrier frequency being varied at a 440 cycle rate.
GPS works in the same way. The pseudo random code has a bit rate of about 1 MHz but its carrier frequency has a cycle rate of over a GHz (which is 1000 times faster!)
At the speed of light the 1.57 GHz GPS signal has a wavelength of roughly twenty centimeters, so the carrier signal can act as a much more accurate reference than the pseudo random code by itself. And if we can get to within one percent of perfect phase like we do with code-phase receivers we'd have 3 or 4 millimeter accuracy! Yeeow!
In essence this method is counting the exact number of carrier cycles between the satellite and the receiver.
The problem is that the carrier frequency is hard to count because it's so uniform. Every cycle looks like every other. The pseudo random code on the other hand is intentionally complex to make it easier to know which cycle you're looking at.
So the trick with "carrier-phase GPS" is to use code-phase techniques to get close. If the code measurement can be made accurate to say, a meter, then we only have a few wavelengths of carrier to consider as we try to determine which cycle really marks the edge of our timing pulse.
Resolving this "carrier phase ambiguity" for just a few cycles is a much more tractable problem and as the computers inside the receivers get smarter and smarter it's becoming possible to make this kind of measurement without all the ritual that surveyors go through.
You've got to hand it to the FAA. They think big!
They realized the great benefits GPS could bring to aviation, but they wanted more. They wanted the accuracy of Differential GPS and they wanted it across the whole continent. Maybe the whole world.
Their plan is called the "Wide Area Augmentation System" or "WAAS," and it's basically a continental DGPS system.
The idea grew out of some very specific requirements that basic GPS just couldn't handle by itself. It began with "system integrity." GPS is very reliable but every once in a while a GPS satellite malfunctions and gives inaccurate data.
The GPS monitoring stations detect this sort of thing and transmit a system status message that tells receivers to disregard the broken satellite until further notice. Unfortunately this process can take many minutes which could be too late for an airplane in the middle of a landing.
So the FAA got the idea that they could set up their own monitoring system that would respond much quicker. In fact, they figured they could park a geosynchronous satellite somewhere over the U.S. that would instantly alert aircraft when there was a problem.
Then they reasoned that they could transmit this information right on a GPS channel so aircraft could receive it on their GPS receivers and wouldn't need any additional radios.
But wait a second! If we've got the geosynchronous satellite already transmitting on the GPS frequency, why not use it for positioning purposes too? Adding another satellite helps with positioning accuracy and it ensures that plenty of satellites are always visible around the country.
But wait another second! Why not use that satellite to relay differential corrections too?
Oh, this is sounding good!
The FAA figured that with about 24 reference receivers scattered across the U.S. they could gather pretty good correction data for most of the country. That data would make GPS accurate enough for "Category 1" landings (i.e. very close to the runway but not zero visibility)
This system is underway. Specifications have been drafted and approved and it's expected that the system could be working as early as 1997.
The ramifications of this go well beyond aviation, because the system guarantees that DGPS corrections will be raining out of the sky for everyone to use.
To complete the system the FAA wants to eventually establish "Local Area Augmentation Systems" near runways.
These would work like the WAAS but on a smaller scale. The reference receivers would be near the runways and so would be able to give much more accurate correction data to the incoming planes.
With a LAAS aircraft would be able to use GPS to make Category 3 landings. (zero visibility)

"Where is everything else?"
It's a big world out there, and using GPS to survey and map it precisely saves time and money in this most stringent of all applications. Today, Trimble GPS makes it possible for a single surveyor to accomplish in a day what used to take weeks with an entire team. And they can do their work with a higher level of accuracy than ever before.
Trimble pioneered the technology which is now the method of choice for performing control surveys, and the effect on surveying in general has been considerable. You've seen how GPS pinpoints a position, a route, and a fleet of vehicles. Mapping is the art and science of using GPS to locate items, then create maps and models of everything in the world. And we do mean everything. Mountains, rivers, forests and other landforms. Roads, routes, and city streets. Endangered animals, precious minerals and all sorts of resources. Damage and disasters, trash and archeological treasures. GPS is mapping the world.
For example, Trimble GPS helped fire fighters respond with speed and efficiency during the 1991 Oakland/Berkeley fire to plot the extent of the blaze and to evaluate damage. In a less urgent yet equally important situation, the city of Modesto, California improved their efficiency and job performance by using GPS and mountain bikes to create a precise map of its network of water resources and utilities.

The Ideas Behind the Jargon
Anywhere fix
The ability of a receiver to start position calculations without being given an approximate location and approximate time.
Bandwidth
The range of frequencies in a signal.
C/A code
The standard (Course/Acquisition) GPS code. A sequence of 1023 pseudo-random, binary, biphase modulations on the GPS carrier at a chip rate of 1.023 MHz. Also known as the "civilian code."
Carrier
A signal that can be varied from a known reference by modulation.
Carrier-aided tracking
a signal processing strategy that uses the GPS carrier signal to achieve an exact lock on the pseudo random code.
Carrier frequency
The frequency of the unmodulated fundamental output of a radio transmitter.
Carrier phase GPS
GPS measurements based on the L1 or L2 carrier signal.
Channel
A channel of a GPS receiver consists of the circuitry necessary to receive the signal from a single GPS satellite.
Chip
The transition time for individual bits in the pseudo-random sequence. Also, an integrated circuit. Also a snack food. Also a betting marker.
Clock bias
The difference between the clock's indicated time and true universal time.
Code phase GPS
GPS measurements based on the pseudo random code (C/A or P) as opposed to the carrier of that code.
Control segment
A world-wide network of GPS monitor and control stations that ensure the accuracy of satellite positions and their clocks.
Cycle slip
A discontinuity in the measured carrier beat phase resulting from a temporary loss of lock in the carrier tracking loop of a GPS receiver.
Data message
A message included in the GPS signal which reports the satellite's location, clock corrections and health. Included is rough information on the other satellites in the constellation.
Differential positioning
Accurate measurement of the relative positions of two receivers tracking the same GPS signals.
Dilution of Precision
The multiplicative factor that modifies ranging error. It is caused solely by the geometry between the user and his set of satellites. Known as DOP or GDOP
Dithering
The introduction of digital noise. This is the process the DoD uses to add inaccuracy to GPS signals to induce Selective Availability.
Doppler-aiding
A signal processing strategy that uses a measured doppler shift to help the receiver smoothly track the GPS signal. Allows more precise velocity and position measurement.
Doppler shift
The apparent change in the frequency of a signal caused by the relative motion of the transmitter and receiver.
Ephemeris
The predictions of current satellite position that are transmitted to the user in the data message.
Fast switching channel
A single channel which rapidly samples a number of satellite ranges. "Fast" means that the switching time is sufficiently fast (2 to 5 milliseconds) to recover the data message.
Frequency band
A particular range of frequencies.
Frequency spectrum
The distribution of signal amplitudes as a function of frequency.
Geometric Dilution of Precision (GDOP)
See Dilution of Precision.
Hardover word
The word in the GPS message that contains synchronization information for the transfer of tracking from the C/A to P code.
Ionosphere
The band of charged particles 80 to 120 miles above the Earth's surface.
Ionospheric refraction
The change in the propagation speed of a signal as it passes through the ionosphere.
L-band
The group of radio frequencies extending from 390 MHz to 1550 MHz. The GPS carrier frequencies (1227.6 MHz and 1575.42 MHz) are in the L band.
Multipath error
Errors caused by the interference of a signal that has reached the receiver antenna by two or more different paths. Usually caused by one path being bounced or reflected.
Multi-channel receiver
A GPS receiver that can simultaneously track more than one satellite signal.
Multiplexing channel
A channel of a GPS receiver that can be sequenced through a number of satellite signals.
P-code
The Precise code. A very long sequence of pseudo random binary biphase modulations on the GPS carrier at a chip rate of 10.23 MHz which repeats about every 267 days. Each one week segment of this code is unique to one GPS satellite and is reset each week.
Precise Positioning Service (PPS)
The most accurate dynamic positioning possible with standard GPS, based on the dual frequency P-code and no SA.
Pseudolite
A ground-based differential GPS receiver which transmits a signal like that of an actual GPS satellite, and can be used for ranging.
Pseudo random code
A signal with random noise-like properties. It is a very complicated but repeating pattern of 1's and O's.
Pseudorange
A distance measurement based on the correlation of a satellite transmitted code and the local receiver's reference code, that has not been corrected for errors in synchronization between the transmitter's clock and the receiver's clock.
Satellite constellation
The arrangement in space of a set of satellites.
Selective Availability (SA)
A policy adopted by the Department of Defense to introduce some intentional clock noise into the GPS satellite signals thereby degrading their accuracy for civilian users. This policy was discontinued as of May 1, 2000 and now SA is turned off
Slow switching channel
A sequencing GPS receiver channel that switches too slowly to allow the continuous recovery of the data message.
Space segment
The part of the whole GPS system that is in space, i.e. the satellites.
Spread spectrum
A system in which the transmitted signal is spread over a frequency band much wider than the minimum bandwidth needed to transmit the information being sent. This is done by modulating with a pseudo random code, for GPS.
Standard Positioning Service (SPS)
The normal civilian positioning accuracy obtained by using the single frequency C/A code.
Static positioning
Location determination when the receiver's antenna is presumed to be stationary on the Earth. This allows the use of various averaging techniques that improve accuracy by factors of over 1000.
User interface
The way a receiver conveys information to the person using it. The controls and displays.
User segment
The part of the whole GPS system that includes the receivers of GPS signals.

Improving the Civilian Global Positioning System

2009-05-11T20:41:00.001-05:00

GPS IS A CRITICAL TECHNOLOGY FOR INDIVIDUALS AND BUSINESSES AROUND THE GLOBE. GPS is a dual-use system, providing highly accurate positioning and timing data for both military and civilian users. There are more than 4 million GPS users world wide, and the market for GPS applications is expected to double in the next three years, from $8 billion to over $16 billion. Some of these applications include: air, road, rail, and marine navigation, precision agriculture and mining, oil exploration, environmental research and management, telecommunications, electronic data transfer, construction, recreation and emergency response.

GPS IS THE GLOBAL STANDARD. GPS has always been the dominant standard satellite navigation thanks to the U.S. policy of making both the signal and the receiver design specification available to the public completely free of charge.

NEW TECHNOLOGIES ENHANCE AMERICA'S NATIONAL SECURITY. The U.S. previously employed a technique called Selective Availability (SA) to globally degrade the civilian GPS signal. New technologies demonstrated by the military enable the U.S. to degrade the GPS signal on a regional basis. GPS users worldwide would not be affected by regional, security-motivated, GPS degradations, and businesses reliant on GPS could continue to operate at peak efficiency.

GPS IMPROVED SIGNAL WILL BRING INSTANT BENEFITS TO MILLIONS OF GPS USERS. The improved, non-degraded signal will increase civilian accuracy by an order of magnitude, and have immediate implications in areas such as:

· Car Navigation: Previously, a GPS-based car navigation could give the location of the vehicle to within a hundred meters. This was a problem, for example in areas where multiple highways run in parallel, because the degraded signal made it difficult to determine which one the car was on. Terminating SA will eliminate such problems, leading to greater consumer confidence in the technology and higher adoption rates. It will also simplify the design of many systems (e.g., eliminate certain map matching software), thereby lowering their retail cost.

· Enhanced-911: The FCC will soon require that all new cellular phones be equipped with more accurate location determination technology to improve responses to emergency 911 calls. Removing SA will boost the accuracy of GPS to such a degree that it could become the method of choice for implementing the 911 requirement. A GPS-based solution might be simpler and more economical than alternative techniques such as radio tower triangulation, leading to lower consumer costs.

· Hiking, Camping, and Hunting: GPS is already popular among outdoorsmen, but the degraded accuracy has not allowed them to precisely pin-point their location or the location of items (such as game) left behind for later recovery. With 20 meter accuracy or better, hikers, campers, and hunters should be able to navigate their way through unmarked wilderness terrain with increased confidence and safety. Moreover, users will find that the accuracy of GPS exceeds the resolution of U.S. Geological Survey (USGS) topographical quad maps.

· Boating and Fishing: Recreational boaters will enjoy safer, more accurate navigation around sandbars, rocks, and other obstacles. Fishermen will be able to more precisely locate their favorite spot on a lake or river. Lobster fishermen will be able to find and recover their traps more quickly and efficiently.

· Increased Adoption of GPS Time: In addition to more accurate position information, the accuracy of the time data broadcast by GPS will improve to within 40 billionths of a second. Such precision may encourage adoption of GPS as a preferred means of acquiring Universal Coordinated Time (UTC) and for synchronizing everything from electrical power grids and cellular phone towers to telecommunications networks and the Internet. For example, with higher precision timing, a company can stream more data through a fiber optic cable by tightening the space between data packets. Using GPS to accomplish this is far less costly than maintaining private atomic clock equipment.

A GPS navigation system built for high Earth orbits

2009-05-10T16:25:00.001-05:00

A GPS navigation system built for high Earth orbits

Until now, Global Positioning System (GPS) receivers, while providing an accurate and inexpensive means of navigation, have been limited to low Earth orbit (LEO) missions. This innovative receiver technology developed by NASA Goddard Space Flight Center is a leap forward for GPS technology.

The Navigator is an autonomous, real-time, fully space-flight-qualified GPS receiver with exceptional capabilities for fast signal acquisition and weak signal tracking. These features enable the use of GPS navigation in high Earth orbit (HEO), geostationary orbit, and other high altitude applications. The Navigator receiver can quickly and reliably acquire and track GPS signals at 25 dB-Hz and lower.

Benefits

Enables GPS in High Earth Orbit: Because it can acquire and track even very weak signals and requires no external data, (e.g., ground station uplinks of position, velocity or time), the Navigator receiver enables use of GPS in high Earth orbits (HEO), geostationary orbits, and other high altitude uses.

Acquires Signals Faster: By employing efficient Fast Fourier Transform (FFT) algorithms and Field Programmable Gate Arrays (FPGA) to implement a massively parallel search, even weak signals can be acquired thousands of times faster than in traditional serial search methods.

Operates Autonomously: With the exception of GPS signals, the receiver requires no external data for operation.

Is robust and reliable: The radiation-hardened receiver can reliably operate in the harsh environment of space. (High altitude orbits can present particularly harsh radiation environments.)

Improves GPS Navigation in LEO: When used in LEO, the receiver’s fast acquisition rate eliminates the approximately 20-minute cold start delay time, acquiring GPS signals in only seconds.

Applications

High altitude spacecraft (e.g., Geostationary Operational Environmental Satellite (GOES), Magneto Multiscale Science (MMS), other geostationary orbit (GEO) satellites)

Low Earth orbit spacecraft (offers enhanced GPS navigation via Navigator's fast-acquisition capability)

Technology Details

Because GPS signals at altitudes above the GPS constellation are 10 to 100 times weaker and less densely populated, GPS receivers have not been feasible for use above LEO. The Navigator is a radiation-hardened GPS receiver specifically designed for use in high Earth orbits. It is capable of significantly faster acquisition times and tracking for both strong and weak signals. It requires no external data, and its fast acquisition enables it to be powered down in any orbit until needed.

How it works

In order to determine positioning using GPS, a receiver must first acquire the GPS signals and then track those signals simultaneously. When tracking the signal, the receiver holds and extracts data, making range measurements from each satellite. Those measurements are processed to determine the position of each satellite and then extrapolate the receiver’s position.

To enable it to acquire GPS signals very quickly and also track weak signals, the radiation-hardened Navigator receiver utilizes a bank of hardware correlators, a ColdFire microprocessor, and a specialized fast acquisition module (see figure 1). The hardware is implemented in VHSIC Hardware Description Language (VHDL) to target radiation-hardened Field Programmable Gate Arrays (FPGA) rather than Application-specific Integrated Circuits (ASIC), in order to maintain flexibility for growth and design modifications.

Autonomous operation

One of the Navigator’s two design principles was autonomous operation to promote the feasibility of using GPS for onboard navigation of geostationary (GEO) or other high altitude space missions. With the exception of GPS signals, Navigator requires no external data (e.g., current estimate of time, recent GPS almanac, or converged navigation filter estimate of the receiver dynamics).

Data processing software

By double buffering data up front in 1ms blocks, data can be processed as it is acquired. A discrete Fourier transform (DFT) is used to calculate the 1 ms correlations. Time is significantly reduced by using a FFT algorithm to compute these DFTs. Computational efficiency is optimized and tradeoffs among sampling rate, data format, and data-path bit rate are carefully weighed in order to increase performance of the algorithm.

In addition, the Navigator’s hardware-independent receiver software includes both a hardware interface to perform low-level functions, such as controlling the acquisition engine and tracking loops as well as basic navigation software. The navigation software runs on the Nucleus real-time operating system and forms measurements; provides standard position, velocity, and time-point solutions (when four or more satellites are being tracked); and handles commanding and telemetry messages. It also is capable of determining attitude when it is set up with an appropriate antenna configuration. Onboard orbit determination and accurate state estimation/propagation during periods with no GPS access are accomplished by integration with the GPS Enhanced Onboard Navigation System (GEONS).

Why it is better

Because of the weakness of GPS signals at altitudes above HEO, there are currently no GPS receivers for use in HEO. The standard acquisition approach is to use a serial search of the two-dimensional signal parameter space (code phase and Doppler), using the same hardware that is used for tracking. Because a serial search cold start acquisition, which means there is no prior information about visible GPS signals, can take as long as 20 minutes for even strong GPS signals, weak signals are essentially impossible to acquire. For example, a signal that is 10 times weaker will require 10 times as much data. But, when using serial search methods, acquisition times increase quadratically making the 20-minute search increase to 33 hours.

Navigator exploits the properties of Fourier transform in a massively parallel search for the GSP signal. Navigator has been tested and proven capable of acquiring signals at 25 dB-Hz and below.

The History of GPS

2009-05-08T17:08:00.000-05:00

For centuries, navigators and explorers have searched the heavens for a system that would enable them to locate their position on the globe with the accuracy necessary to avoid tragedy and to reach their intended destinations. On June 26, 1993, however, the answer became as simple as the question. On that date, the U.S. Air Force launched the 24th Navstar satellite into orbit, completing a network of 24 satellites known as the Global Positioning System, or GPS. With a GPS receiver that costs less than a few hundred dollars you can instantly learn your location on the planet--your latitude, longitude, and even altitude--to within a few hundred feet.

This incredible new technology was made possible by a combination of scientific and engineering advances, particularly development of the world's most accurate timepieces: atomic clocks that are precise to within a billionth of a second. The clocks were created by physicists seeking answers to questions about the nature of the universe, with no conception that their technology would some day lead to a global system of navigation. Today, GPS is saving lives, helping society in countless other ways, and generating 100,000 jobs in a multi-billion-dollar industry.

What is GPS? How Does it Work?

2009-05-07T06:19:00.001-05:00

The Global Positioning System (GPS) tells you where you are on Earth.

It's eleven o'clock ... do you know where your kids are? Would you like to? One way to track them would be to have a GPS receiver installed in the car! The GPS, or Global Positioning System, is one of the hottest technologies around, and no wonder. Consider these diverse uses:

Minnesota scientists use GPS to study movements and feeding habits of deer.
Surveyors used GPS to measure how the buildings shifted after the bombing in Oklahoma City.
GPS help settle property disputes between land owners.
Marine archaeologists use GPS to guide research vessels hunting for shipwrecks.
GPS data has revealed that Mt. Everest is getting taller!

GPS answers five questions simultaneously:

"Where am I?"
"Where am I going?"
"Where are you?"
"What's the best way to get there?
"When will I get there?"

GPS is the only system today that can show your exact position on the Earth anytime, in any weather, no matter where you are!

Development:
Like so many other high-tech developments, GPS was designed by the U. S. military. The concept started in the late '60s but the first satellite wasn't launched until February 1978. In 1989 the Magellan Corp. introduced the first hand-held GPS receiver. In 1992 GPS was used in Operation Desert Storm. On March 1996 the President decided to make GPS free for civilian users.

System Description:
GPS has three 'segments':

The space segment now consists of 28 satellites, each in its own orbit about 11,000 nautical miles above the Earth.
The user segment consists of receivers, which you can hold in your hand or mount in your car.
The control segment consists of ground stations (five of them, located around the world) that make sure the satellites are working properly.

Civilian Use:
At first, the military did not want to let civilians use GPS, fearing that smugglers, terrorists, or hostile forces would use it. Finally, bowing to pressure from the companies that built the equipment, The Defense Department made GPS available for non-military purposes, with some restrictions. On May 1, 2000, President Clinton lifted the restrictions, and announced that the option to degrade civil GPS signals during emergencies would be phased out by 2010. The federal government is committed to providing GPS technology for peaceful uses on a worldwide basis, free of charge.

Geocaching

2009-05-06T14:27:00.000-05:00

A GPS device and a hunger for adventure are all you need for high tech treasure hunting. At www.geocaching.com, you will find the latest treasures, or “caches,” in your area, how to hide your own cache, and information on how to get started in this fun and exciting sport. Geocaching is an entertaining adventure game for Global Positioning Systems (GPS) users. Participating in a cache hunt is a good way to take advantage of the wonderful features and capability of GPS receivers. Educators could hide geocaches with their students right on the school grounds!

Individuals and organizations have set up caches all over the world and share the locations of these caches on the Internet. GPS users can then use the location coordinates to find the caches. Once found, a cache may provide the visitor with a wide variety of rewards. All the visitor is asked to do is if they take something from the cache, they should try to leave something for the cache.

The word “Geocaching” represents geo for geography, and caching for the process of hiding a cache. A cache is used in hiking, exploring, and camping as a hiding place for concealing and preserving provisions.

GPS is all around us: Archaeologists use GPS to mark dig sites and specific artifacts within them, historians use GPS to map historic sites, military historians use GPS to mark troop movements on battlefields, genealogists use GPS to mark gravesites and abandoned cemeteries, cartographers use GPS for mapmaking, E-911 crews use GPS to find accidents and residences, utilities personnel use GPS to map and plan gas and electric lines, and thousands more applications exist. What better way to have students conduct field investigations than by using the same tool that these scientists, engineers, and other professionals use everyday on the job?

As of early 2006 , there were 250,000 active caches in 221 countries. During a recent week, over 172,000 new logs were written by 27,000 account holders.

Educational Applications

Students can learn about the following through Geocaching:

Geography--coordinate systems (latitude and longitude, and other coordinate systems such as UTM and state plane), maps, and become familiar with the school grounds, local area, or region.

Mathematics—angles, distances, triangulation, and direction.

Field Work—How to work in the field and collect meaningful data.

Site for Using GPS for Math, Science & Social Studies Instruction:

http://groups.yahoo.com/group/nygps/

GPS to GIS

2009-05-05T12:59:00.002-05:00

GPS To GIS

Using GPS in the educational curriculum is an excellent way to introduce interdisciplinary topics with students, incorporate meaningful field experiences, make effective use of technology, provide employment skills, and illustrate the importance of precision, coordinate systems, relative versus absolute location, and to map local and regional phenomena, such as trees, historical housing, bird nests, and other features. GPS activities may be greatly enhanced by importing these coordinates and field-collected data into a GIS (Geographic Information System). This document describes ways to bring GPS coordinates into a GIS.

There are 2 main methods to bring your GPS coordinates into a GIS, such as ArcView GIS by ESRI:

1. Collect points, write them down, and manually enter into a Notepad file via a text editor or into Excel.

2. Collect points, store inside GPS unit, and with cable, upload the points into the computer, into either a DBF or a TXT file, or even as a GIS-ready file (such as a Shapefile (SHP)).

Method 1: Text Editor

Collect points and attributes. In text editor, line 1 should be the header line, such as "lat, long, pH, groundcover, O2, etc". Line 2 begins your data, separated by commas, such as "site1, 39.7022, -107.4832, 5.7, grassland, 38" Save as Text such as "gps.txt".

Access ArcView 3: Tables-->Add, Add your table gps.txt as comma-delimited TXT. View. Add event theme. Bring in your table as a point theme.

Access ArcGIS 9: Tools--> Add XY coordinates. Add your table gps.txt as text file. Bring in your table as a point layer.

Click on layer to make visible. Change legend to make graduated symbol map based on attributes you collected.

Method 1: Spreadsheet

Collect points and attributes. In Excel, row 1 should be the header line, such as "lat, long, pH, groundcover, O2, etc". Row 2 begins your data, such as "site1, 39.70224, -107.48372, 5.7, grassland, 38" Make sure you format the latitude and longitude columns as numbers with at least 6 decimal places. Save as DBF such as "gps.dbf".

Access ArcView 3: Tables--> Add, Add your table gps.dbf as Dbase file. View --> Add event theme. Bring in your table as a point theme.

Access ArcGIS 9: Tools--> Add XY coordinates. Add your table gps.dbf as Dbase file. Bring in your table as a point layer.

Click on layer to make visible. Change legend to make graduated symbol map based on attributes you collected.

Method 2: Upload Coordinates from GPS

Collect points, store inside GPS unit, upload via cable into computer. This method varies depending on the type of GPS hardware you own. The following procedures work with Garmin receivers. Use other software with other GPS receivers.

Why use method 2 versus manually collecting points and and entering them into a text file?

To (1) reduce error in transcription and recording;

and

(2) to expedite the process, particularly if you students are collecting many points.

1. Clear previous waypoints on GPS unit. Make sure interface says Garmin to Garmin.

2. Use mark and save on GPS unit at each new point collected.

3. Download and run the Garmin tool from the Minnesota Department of Natural Resources:

http://www.dnr.state.mn.us/mis/gis/tools/arcview/extensions/DNRGarmin/DN RGarmin.html

4. Use serial or USB cable to connect your GPS unit to your computer. Turn on your GPS unit.

5. Run MN DNR Garmin extension.

Waypoints: Download.

Tracks: Download.

Output shape file: Point (could use line or poly, too).

Using ArcGIS?

Try the GPSi in ArcGIS. Download it from: http://arcscripts.esri.com/details.asp?dbid=12749

GPSi (GPS Interface) is an ArcMap Toolbar that allows users to communicate with Garmin * handheld GPS units. It was developed to allow users to rapidly download/upload data directly from ArcMap. The software uses the Garmin protocol to communicate with the GPS unit and will not function with other GPS brands.

Additional Notes

I collected in NAD 27 and placed the points on top of a USGS DRG in NAD 27. Why were the points all shifted to the west of where they should be? I thought initially that I was wrong about the datum of the DRGs I was using, but most of the DRGs are indeed in NAD 27 unless they’re from Terraserver.

Here is what apparently caused it: In the Waypoint software itself, there is a setting where the user must explicitly choose NAD 27. If you don't select this, it apparently shifts the coordinates to NAD 83, even though those I was training collected in NAD 27 on the GPS unit! So, make sure you check this if you're automatically uploading using WayPoint in the future. When I did this, the points plotted right where they were supposed to.

Also – There IS a setting in Waypoint that allows the points to be brought in as UTM, rather than importing them in as Lat-Long. This will allow you to view the points table (or lines or polygons if you choose to bring them in as such) as UTM, negating the need to change the view properties to UTM in ArcView.

Either collect in latitude/longitude or UTM. If lat/long, and if you use a USGS DRG or DOQ, you must change the VIEW properties in order to view these correctly on top of the base layers. If you collect in UTM, no view properties setting is required.

Base Map Images

For base map images of USGS topographic maps and aerial photographs to place behind your GPS collected coordinates in a GIS. See complete procedures, as well as new ESRI Terraserver tool, on:

http://education.usgs.gov/common/lessons/terraserver.html

(1) Visit www.terraserver-usa.com. Type in a specific place and press “Go.”

(2). First, select a TOPOGRAPHIC MAP of the area you are interested in. Continue zooming and panning until the area you want is in the view. Make the image size LARGE using the button above the map. You can zoom in until the zoom factor is 2 meters.

(3). Select DOWNLOAD in the upper right hand corner of the image. Click on the FREE DOWNLOAD arrow to redraw the image.

(4) After the image has redrawn, right-click on the image and SAVE AS .jpg

For example, oakcliff_drg.jpg

(5) Click on the WORLD FILE link to open the registration file for the image in the browser window.

Go to FILE —> SAVE AS .jgw For example, oakcliff_drg.jgw

Be sure to save this as a TEXT file, not HTML. Also, it must have the same base name as your JPG file, above.

(6). Go back to the browser window where your topographic map is (before you downloaded it). Click on IMAGE to see a DOQ of that same area. (Note—92% of the country has images on Terraserver at present). The procedures for the DOQ are similar to that for the DRGs that you followed above. Make sure the image is LARGE.

(7). Select DOWNLOAD in the upper right hand corner of the image. You will see a screen similar to that below. Click on the FREE DOWNLOAD arrow to redraw the image.

(8). After the image has redrawn, right-click on the image and SAVE AS .jpg

For example, oakcliff_doq.jpg.

(9) Click on the WORLD FILE link to open the registration file for the image in the browser window. Go to FILE —> SAVE AS .jgw. Be sure to save this as a TEXT file, not HTML.

For example, oakcliff_doq.jgw Also, it must have the same base name as your JPG file, above.

(10). In ArcView, turn on the JPG reader extension and add your images as IMAGE THEMES.

If they do not appear, be sure to check your file names on your system.

Even easier is to use the ESRI Terraserver tool, described on: http://education.usgs.gov/common/lessons/terraserver.html

2009-05-05T12:59:00.001-05:00

There are 2 main methods to bring your GPS coordinates into a GIS, such as ArcView GIS by ESRI:

1. Collect points, write them down, and manually enter into a Notepad file via a text editor or into Excel.

2. Collect points, store inside GPS unit, and with cable, upload the points into the computer, into either a DBF or a TXT file, or even as a GIS-ready file (such as a Shapefile (SHP)).

Method 1: Text Editor

Access ArcGIS 9: Tools--> Add XY coordinates. Add your table gps.txt as text file. Bring in your table as a point layer.

Click on layer to make visible. Change legend to make graduated symbol map based on attributes you collected.

Method 1: Spreadsheet

Access ArcView 3: Tables--> Add, Add your table gps.dbf as Dbase file. View --> Add event theme. Bring in your table as a point theme.

Access ArcGIS 9: Tools--> Add XY coordinates. Add your table gps.dbf as Dbase file. Bring in your table as a point layer.

Click on layer to make visible. Change legend to make graduated symbol map based on attributes you collected.

Method 2: Upload Coordinates from GPS

Why use method 2 versus manually collecting points and and entering them into a text file?

To (1) reduce error in transcription and recording;

and

(2) to expedite the process, particularly if you students are collecting many points.

1. Clear previous waypoints on GPS unit. Make sure interface says Garmin to Garmin.

2. Use mark and save on GPS unit at each new point collected.

3. Download and run the Garmin tool from the Minnesota Department of Natural Resources:

http://www.dnr.state.mn.us/mis/gis/tools/arcview/extensions/DNRGarmin/DN RGarmin.html

4. Use serial or USB cable to connect your GPS unit to your computer. Turn on your GPS unit.

5. Run MN DNR Garmin extension.

Waypoints: Download.

Tracks: Download.

Output shape file: Point (could use line or poly, too).

Using ArcGIS?

Try the GPSi in ArcGIS. Download it from: http://arcscripts.esri.com/details.asp?dbid=12749

Additional Notes

Base Map Images

For base map images of USGS topographic maps and aerial photographs to place behind your GPS collected coordinates in a GIS. See complete procedures, as well as new ESRI Terraserver tool, on:

http://education.usgs.gov/common/lessons/terraserver.html

(1) Visit www.terraserver-usa.com. Type in a specific place and press “Go.”

(3). Select DOWNLOAD in the upper right hand corner of the image. Click on the FREE DOWNLOAD arrow to redraw the image.

(4) After the image has redrawn, right-click on the image and SAVE AS .jpg

For example, oakcliff_drg.jpg

(5) Click on the WORLD FILE link to open the registration file for the image in the browser window.

Go to FILE —> SAVE AS .jgw For example, oakcliff_drg.jgw

Be sure to save this as a TEXT file, not HTML. Also, it must have the same base name as your JPG file, above.

(7). Select DOWNLOAD in the upper right hand corner of the image. You will see a screen similar to that below. Click on the FREE DOWNLOAD arrow to redraw the image.

(8). After the image has redrawn, right-click on the image and SAVE AS .jpg

For example, oakcliff_doq.jpg.

(9) Click on the WORLD FILE link to open the registration file for the image in the browser window. Go to FILE —> SAVE AS .jgw. Be sure to save this as a TEXT file, not HTML.

For example, oakcliff_doq.jgw Also, it must have the same base name as your JPG file, above.

(10). In ArcView, turn on the JPG reader extension and add your images as IMAGE THEMES.

If they do not appear, be sure to check your file names on your system.

Even easier is to use the ESRI Terraserver tool, described on: http://education.usgs.gov/common/lessons/terraserver.html

Helpful GPS Tips

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Helpful GPS Tips

KEEP YOUR UNIT IN 3-D MODE. Some models are locked into 3-D and do not permit you to toggle between 3-D and 2-D modes.
RE-INITIALIZE YOUR GPS UNIT IF YOU’VE TRAVELED SEVERAL HUNDRED MILES. This will make acquiring a position fix faster. Some models automatically perform this step.
ALWAYS VERIFY YOU’RE USING THE CORRECT MAP DATUM, ELEVATION MODE, NORTH INDICATOR, AND COORDINATE SYSTEM. Some models will default back to manufacturer’s specifications when the unit is turned off.

KEEP THE ANTENNA POINTED SKYWARD FOR BEST RECEPTION.
ALWAYS VERIFY YOU’RE RECEIVING ENOUGH SIGNALS (via the satellite status screen) BEFORE MAKING CRITICAL NAVIGATIONAL DECISIONS.
ALWAYS CARRY SPARE BATTERIES.

PRACTICE YOUR GPS SKILLS IN SAFE, FAMILIAR SURROUNDING BEFORE GOING INTO THE WILDERNESS.

DON’T USE THE BACKLIGHT FUNCTION UNTIL NEEDED-IT WILL DRAIN YOUR BATTERIES.

YOU MAY SET YOUR GPS TO THE UTM COORDINATE SYSTEM & ALSO SET YOUR GPS NAVIGATIONAL UNITS TO STATUE MILES. This will allow you to use the metric-based UTM coordinate system, but display navigational distances in feet.

BEFORE HIKING IN THE WILDERNESS, IT’S A GOOD IDEA TO TAKE A GPS WAYPOINT AT YOUR CAR. This way, you’ll always know the straight-line distance & direction back to safety.

GIVE YOUR GPS WAYPOINTS INTUITIVE NAMES. For example, if hiking in Pike National Forest, name them PNF1, PNF2, PNF3, etc.

GPS VOCABULARY & ABBREVIATIONS:

BEARING: this is the direction your GPS wants to you to follow

HEADING: this is the direction you’re actually following
XTE: cross-track error, this is your GPS unit’s estimate of the direction & distance you are deviating from the BEARING it wants you to follow
TRUE NORTH: bearings are adjusted for local magnetic declination
MAGNETIC NORTH: bearings are NOT adjusted for local magnetic declination

Adjustable Declination Compass

A Compass with adjustable declination allows you to rotate the orienting arrow independently of the compass dial. If you have such a compass, you may calculate your map bearing without adding or subtracting the amount of local magnetic declination. To calibrate your compass in this fashion, rotate the inner liquid capsule (or turn the screw with the key) until the orienting arrow deviates from the compass ring’s north indicator by the amount & direction of the local magnetic declination. For example, if local declination is 10 degrees east of true north, rotate the inner liquid capsule (or turn the screw with the key) until the orienting arrow points to 10 degrees east.

How Should I Set My GPS and Compass?

Let’s assume the local declination is 10 degrees east of true north, and the waypoint you wish to navigate to is directly north of your current location.

If using a compass without adjustable declination (the orienting arrow cannot be adjusted – it always points to North on the compass dial), set your GPS to magnetic north. Your GPS will indicate a bearing of 350 degrees must be followed to reach the waypoint. Dial 350 degrees at the index line on your compass. With the direction-of-travel arrow pointed directlyaway from you, turn your body & compass in one motion until the red magnetic needle overlays the orienting arrow. Site a landmark along that bearing, and proceed. You will be traveling directly north toward the waypoint.

If using a compass with adjustable declination, set your GPS to true north. Your GPS will indicate a bearing of zero degrees must be followed to reach the waypoint. Adjust the declination on your compass so the orienting arrow points to 10 degrees east. Dial zero degrees at the index line on your compass. With the direction-of-travel arrow pointed directlyaway from you, turn your body & compass in one motion until the red magnetic needle overlays the orienting arrow. Site a landmark along that bearing and proceed. You will be traveling directly north toward the waypoint.

Setting the Correct Datum and Coordinate System

GPS receivers internally store coordinates in the “Earth-Centered, Earth-Fixed (ECEF) Coordinate System.” These coordinates never appear on your screen, but receivers use this system because it permits fast, accurate distance and direction calculation. When automatically capturing waypoints in the field, your GPS can be set to any datum and coordinate system. When recalling those coordinates from memory, the receiver will convert them from ECEF to the datum and coordinate system you specify. When manually entering waypoints you’ve calculated from a map; however, make sure your GPS is setup to match the map’s datum.

Questions and Answers About GPS

2009-05-03T07:08:00.000-05:00

1. What do I need to know to get my GPS into correct operation?

We generally emphasize the following four points:

1. Select a coordinate system. We usually suggest using either the Universal Transverse Mercator System (UTM) or latitude/longitude. Using UTM results in easier plotting on the USGS 7.5’ quadrangle maps. The coordinate system displayed by your GPS is usually just a position format selection on your unit’s navigation set up page.

2. Select the correct horizontal datum. Most GPS units default to a datum called the World Geodetic System of 1984 (WGS84). However, most USGS maps are referenced to a different datum, the North American Datum of 1927 (NAD27). A few USGS maps are set to the North American Datum of 1983 (NAD83), which is virtually identical to WGS84. Check the map information at the lower left corner of the USGS 7.5’ quadrangle to determine the correct datum used in the making of the map. Correct datum is especially important if you are using the UTM coordinate system. Your GPS setup menu may present several variations of NAD27 to select from; most users will select NAD27 CONUS, which is appropriate for the CONtinentalUS.

3. Be aware that the vertical heights displayed by your recreational GPS receiver will not agree well with USGS map elevations. The main reasons for this discrepancy is the inherent poor fix geometry available for vertical determinations (the earth is always blocking some of the desired satellites) and the use of different reference surfaces for the vertical measurement. DO NOT USE GPS ELEVATIONS FOR CRITICAL NAVIGATION DECISIONS.

4. Select which “North” your GPS receiver will use as the zero degree reference. The default in your receiver is probably true north = 0 degrees. You can also select magnetic north = 0 degrees or grid north (north-south lines of the UTM grid) = 0 degrees. Many users select magnetic north as zero degrees so they can follow a compass bearing without converting the azimuth to true north. Many GPS units automatically calculate the local magnetic variation (declination) for the fix time and date.

2. How do I locate a point in latitude and longitude on a USGS 7.5' quadrangle?

To accurately plot a latitude/longitude position, the map reader must first connect the 2.5’ ticks encompassing the area within which the point will be measured. Using a specially incremented scale, an engineers scale, or a variable scale template, the reader can accurately plot the latitude/longitude of a point.

3. What does the term UTM mean?

UTM is the acronym for Universal Transverse Mercator, a plane coordinate grid system named for the map projection on which it is based (Transverse Mercator). The UTM system consists of 60 zones, each 6-degrees of longitude in width. The zones are numbered 1-60, beginning at 180-degrees longitude and increasing to the east. The military uses their own implementation of the UTM system, called the Military Grid Reference System (MGRS).

4. Why don't USGS maps show the UTM grid?

Through time, policies have changed regarding whether or not a full UTM grid would appear on the 7.5’ map series. Beginning in the mid 1950’s, the grid was indicated by blue ticks around the projection at 1000 meter spacing. In 1979, the ticks were replaced with a full-line black UTM grid. Because so many complaints were received through a 1991 user survey, the full grid was removed in early 1992. Blue ticks returned to the maps. In 1994, another survey indicated that either a complete grid or internal 1000 meter ticks were the preferred treatment as opposed to the perimeter ticks alone. Once again, a full grid will appear on the 7.5’ series with the exception of single edition quadrangles published cooperatively with the U. S. Forest Service.

5. How are UTM coordinates measured on the quadrangle?

UTM coordinates are measured on the map by subdividing the 1000 meter grid squares into tenths or hundredths. This will narrow down the coordinate to a 100 or 10 meter square. Usually the measurements are made using a simple mylar or paper scale or a coordinate reader. Note that the large numbers that are located adjacent to the tick marks around the perimeter of the map represent tens of thousand and thousands of meters. The millions and hundreds of thousands of meters are shown with small numbers and are sometimes dropped when giving UTM coordinate positions. The military implementation of UTM (MGRS) drops the small digits and indicates the 100,000 meter square by a two letter identifier. Most UTM users and GPS units use the full value of the UTM coordinates.

6. What do the leading numbers and letters mean on my GPS UTM coordinate display (e.g. 13S)?

The number refers to the UTM zone as described above; the letter refers to an 8 degree band of latitude within the specific UTM zone. The southernmost band from 80 degrees South to 72 degrees South is letter "C". The letters increment to the North ending in "X" which is a 12 degree band from 72 degrees North to 84 degrees North. The system skips certain letters which may be confused with numbers, such as the letters “O” and “I”.

7. Why doesn't Grid North correspond to True North?

Grid North pertains to the north for a specific plane coordinate system. All north-south lines run parallel to one another in the UTM projections. True North refers to geodetic or geographic north pole, and the lines of longitude converge on the 7.5’ maps. Because the 7.5’ maps mix the UTM and conic projections occasionally the UTM grid will appear at a small angle to the neatlines (a line separating the body of a map from the map margin) of the map. This is not a cause for concern so long as the UTM grid has been drawn in correctly by the user.

8. How do I report a position?

If coordinates are to be passed on to another person it is technically necessary to report the horizontal datum and the latitude/longitude of the point (e.g. NAD 27 CONUS, 44 degrees, 7 minutes, 30 seconds north/ 104 degrees, 15 minutes, 10 seconds west). If using UTM, include datum, grid zone number, row indicator, easting and then the northing value (e.g. NAD 83/13 S/ 0404524E/ 4239242N). UTM coordinates are always read to the right and up. Different needs may dictate different reporting schemes.

9. Which is the best or more accurate system, the UTM or the latitude/longitude coordinate system?

One system is no more or less accurate than the other. They are just two different ways of positioning a point. Many experienced users prefer UTM over latitude/longitude when using 7.5’ topographic quadrangle maps. Ocean going sailors and other marine users almost always use latitude/longitude because navigation charts are optimized for this method.

10. How can I get more information on any of these coordinate systems and GPS in general?

Many excellent references can be found in standard textbooks. More and more information is being posted on the internet. Refer to the attached lists for specific web sites.

11. How much distance does a degree, minute and second cover on your maps?

The distances vary. A degree, minute or second of latitude remains fairly constant from the equator to the poles; however a degree, minute, or second of longitude can vary greatly as one approaches the poles (because of the convergence of the meridians). At 38 degrees North latitude, one degree of latitude equals approximately 364,000 ft (69 miles), one minute equals 6068 ft (1.15 miles), one-second equals 101 ft; one-degree of longitude equals 288,200 ft (54.6 miles), one minute equals 4800 ft (0.91 mile), and one second equals 80 ft.

12. How do I convert UTM coordinates to latitude/longitude values or vice versa?

Of course, your GPS unit will convert coordinates for you by simply toggling from UTM to lat/long. The USGS uses computer programs to easily convert between UTM and latitude/longitude. One program that is available is Tri_con (Windows 95) or Geocon (DOS) which can be downloaded for free at http://rockyweb.cr.usgs.gov/software

13. Why don't USGS map coordinates agree with those I obtain with my GPS receiver?

There are two main reasons why this may occur. First, be sure your GPS receiver is set to the correct horizontal datum. Experience has shown that the position differences between NAD27 and NAD83 (WGS84) can vary by as much as 100 meters in easting and several hundred meters in northing. In latitude/longitude the maximum error may approach 200 meters.

14. Why don't the elevations on USGS maps agree with those provided by my GPS system? Which ones are correct?

GPS heights are based on an ellipsoid (a mathematical representation the earth’s shape), while USGS map elevations are based on a vertical datum tied to the geoid (or what we commonly call mean sea level). Basically they are two different systems, although they have a relationship which has been modeled. The main source of error has to do with the arrangement of the satellite configurations during fix determinations. The earth blocks out satellites needed to get a good quality vertical measurement. Once the vertical datum is taken into account, the accuracy permitted by geometry considerations remains less than that of horizontal positions. It is not uncommon for satellite heights to be off from map elevations by +/- 400 ft. Use these values with caution when navigating. GPS units do not replace basic map and compass skills!

15. Why are the NAD 83 position values so far from the NAD 27 values? Were the old coordinates wrong?

The old coordinates were not wrong, just different. They are based on different earth shapes or ellipsoids. They were based on the best technology at the time. Mathematically, NAD83 is a stronger datum because all previously existing horizontal stations and newer GPS surveyed stations were adjusted simultaneously. The positions within NAD27 were adjusted in arcs, as the networks progressed across the country. Errors between stations adjusted in different arcs could have been substantial.

16. How will the change in Selective Availability (SA) degradation affect the accuracy of the positions I obtain with my stand alone GPS receiver?

On May 2, 2000, Selective Availability (SA) was turned off. This allows the stand alone GPS receiver to obtain real time accuracies in the range of 10-20 meters rather than the 100 meters available when SA is operating. Further accuracies will be obtained with the addition of a second and third civilian frequency. However, this will not occur until a sufficient number of new BLOCK IIR satellites have been launched. This may not occur until 2006.

17. What happens if a satellite goes bad or new satellites are placed in orbit? Will I have to get a new receiver or have my present device recalibrated?

A satellite could temporarily be bad (the military could be adjusting its orbit or updating the transmitted information). Sometimes the user must be able to look at the screen and determine if the information looks reasonable. The GPS receiver can detect if a satellite is unhealthy and reject the signal from position computations. If a satellite has gone bad, the military will shut it down until the problem has been fixed. If the damage is irreparable, the satellite will be turned off and withdrawn from use. If new satellites are placed in orbit, the receiver will be able to pick them up once the satellites have been declared operational and have transmitted their unique identifying almanac and ephemeris information.

18. Which makers/systems do you recommend?

We cannot recommend individual makers/systems. Some of the major manufacturers are Trimble Navigation, Magellan, Ashtech, Garmin, and Rockwell. Other electronic firms are continually entering the GPS market.

19. How is the State Plane Coordinate system set up? Can GPS provide coordinates in these values? What about Public Land Survey System (PLSS) readouts?

The State Plane Coordinate System (SPCS) is a plane coordinate system (N-S and E-W lines are perpendicular) in which each individual state has from one to six zones, depending on the state's size and shape. The grid system in some states is based on the Lambert Conformal Conic Projection, while the system for other states is based on the Transverse Mercator Projection. As a general rule-of-thumb, states that are longer east - west than north - south use Lambert, while states that are longer north - south use Transverse Mercator. The most notable exception to this is California, which is based on Lambert.

For NAD27, all coordinates were based on U. S. Survey Feet. USGS 7.5’ maps show 10,000 foot black grid ticks along the perimeter of the map. The appropriate zone is listed in the margin data at the lower left-hand corner of the map.

For NAD83, coordinates may be in meters, U. S. Survey Feet, or International Feet depending on the State. Each State was allowed to choose which unit of measure they wanted for surveys within their boundaries. Some states changed origins for their State Plane Coordinate System when switching from NAD27 to NAD83. For these reasons, using this grid system has become less popular than in the past.

Some Trimble professional grade GPS receivers are capable of providing positions in the State Plane Coordinate System. Of course, latitude/longitude or UTM positions recorded in the field or post processed in a computer, can be transformed to SPCS through the computer software mentioned above in question 12.

GPS cannot provide readouts in the Public Land Survey System (PLSS). Points can be plotted onto a map in lat/long or UTM. From that position a user can determine the Section that encompasses the point.

20. How do I get my coordinates off the GPS units and onto my computer for further analysis?

(1) Obtain and plug in a cable that connects your GPS with either the serial or a USB port in your computer.

(2) Upload the coordinates using the software that came with your GPS or one below.

A popular free downloadable extension that turns Garmin GPS data into text files and also ESRI GIS-compatible files:

http://www.dnr.state.mn.us/mis/gis/tools/arcview/extensions/DNRGarmin/DNRGar min.html

An inexpensive GPS download software product: http://www.oziexplorer.com/

A freeware GPS download software product, Waypoints +: http://www.tapr.org/~kh2z/Waypoint/

(3) From the resulting table of latitude-longitude coordinates, map the coordinates in your GIS. In ArcGIS, use the Add XY function.

GPS Sites and Resources

2009-05-02T06:59:00.001-05:00

This is an informal collection of websites we have found to be interesting or useful. Commercial sites
are shown on this list for information purposes only. No endorsement is expressed or implied.
All URLs are http:// sites unless otherwise specified.

Applied Field Data Systems	www.afds.net
Buy GPS Items Online	www.gpsnow.com
Buy GPS Items Online	www.gpsoutfitters.com
Degree Confluence Project	www.confluence.org
DeLorme homepage	www.delorme.com
DGPS- Omnistar	www.omnistar.com
FAA-GPS	gps.faa.gov
Forest Service GPS Page	www.fs.fed.us/database/gps
Fish & Wildlife Service GPS Page	www.fws.gov/data/gps.html
Free Software Upload & Download	www.gpsu.co.uk
Fugawi Moving Map Software	www.fugawi.com
Garmin GPS Homepage	www.garmin.com
GeoCaching	www.geocaching.com
Geodetic Tool Kit	www.ngs.noaa.gov
Geographic Names Information System	geonames.usgs.gov/index.html
GPS Drawings	www.gpsdrawing.com
GPS Drawings	www.gpsinformation.net
GPS World Magazine	www.gpsworld.com
GPS Outfitters	www.gpsoutfitters.com
GPS Visualizer	www.gpsvisualizer.com
Guidepost Services	www.guidepostservices.ca
Joe Mehaffey and Jack Yeazel GPS Info	joe.mehaffey.com
Latitude/Longitude Converter	www.cellspark.com/UTM.html
Make Your Own Maps - Map Tools	www.makeyourownmaps.com
Map Tools	www.maptools.com
Magellan GPS Homepage	www.magellangps.com/en
MapBlast Maps	www.mapblast.com
Marine Chart Source	www.noaa.gov/charts.html
National Geodetic Survey	www.ngs.noaa.gov
Navtech GPS Supply	www.navtechgps.com
NAVSTAR GPS homepage (Military)	tycho.usno.navy.mil/gpsinfo.html
Navtech GPS Supply-GPS Websites	www.navtechgps.com/links.asp
North Magnetic Pole Information	www.geolab.nrcan.gc.ca/geomag/northpole_e.shtml
OziExplorer Mapping Software	www.oziexplorer.com
Russian Space Forces (Glonass)	www.glonass-center.ru/frame_e.html
Space Environ Ctr-homepage	www.sec.noaa.gov
Topozone	www.topozone.com
Trails Illustrated	maps.nationalgeographic.com/trails
Trimble Navigation-GPS homepage	www.trimble.com
UTexas & UColorado GPS Overview	www.colorado.edu/geography/gcraft/notes/gps/ gps_f.html
Upside Down Map of the World	www.flourish.org/upsidedownmap
US Coast Guard Navigation Center	www.navcen.uscg.gov
USGS Homepage	www.usgs.gov
USGS Conversions	rmmcweb.cr.usgs.gov/software
USGS Digital Product Sales	edcsns17.cr.usgs.gov/EarthExplorer
WAAS Information	gps.faa.gov/programs/index.htm
Waypoint Enterprises, Inc.	www.waypoint-ent.com
Wormley Educational Observatory Institude	www.edu-observatory.org/gps/gps.html

GPS in Education

2009-05-01T07:13:00.001-05:00

GPS is an excellent, multidisciplinary, inquiry-driven, field-based, standards-based tool applicable to many subjects, including mathematics, geography, earth science, environmental studies, and more. Ideas for using it in the educational curriculum follow.

Begin the GPS discussion with a base of familiar objects and concepts: Ask the students, "if I were to tell you that I was 10 feet from the far wall in the room, where could I be?" The answer is anywhere on a straight line that is 10 feet from the wall.

Next, "If I were 10 feet from this wall and 5 feet from this wall, now where could I be?" The answer is a single point, at the intersection of the 2 lines. Next, "If I were 10 feet from [Maria]" - answer - circle with a radius of 10 feet, from Maria. Next, "If I were 10 feet from [Maria] and I could be floating in space?" Answer: a sphere with a radius of 10 feet, centered on Maria. If they understand THAT, then it is not a big leap to the following: We can determine that we are 11,002 miles from GPS satellite A, 10,887 miles from satellite B, and so on. The intersection of all those spheres is our current location.

Base the discussion on mathematics. GPS is one of the best real-world examples of how distance=rate * time works. The time is the critical component, that's why GPS was made possible by accurate time pieces, since
the time from the satellite to the receiver is miniscule and needed to be accurately measured. The rate is the speed of light. So the distance is computed by the time diff between the receiver and the satellite. I would
print some of the pages from http://www.howstuffworks.com/gps1.htm or the Geographer's Craft pages at
http://www.Colorado.EDU/geography/gcraft/notes/gps/gps_f.html to aid your discussion and diagrams.

Use GPS coordinates to help explain the lat-long and the UTM coordinates on any USGS topographic map of the area you're collecting the points in. Walk with the GPS and pose questions such as, "why do the
northings on UTM decrease as you're walking south?"

Have students, in teams, determine the location of the school grounds [or wherever you're collecting] on a USGS 24K topo map, via manual interpolation, in both lat-long and UTM. Then go out and collect coordinates. Which team was closest? What about the vertical elevation? Don't be too hasty on dropping the manual interpolation for the GPS reading, especially on the vertical. This is because GPS readings for elevation may be less accurate than what students can interpolate from the topographic map. It lends itself for a good discussion on being critical of the data you are working with; know where it came from, and know its benefits and limitations.

Discuss the vertical and horizontal datums in conjunction with GPS and tie the lesson to the mathematics standards.

Set up a virtual geocaching course around the campus or off campus. Make the geocaches virtual so that (1) you are not littering the landscape with boxes; (2) there is no danger that someone else could take your geocache, and (3) students find things that exist permanently on the landscape - reading a number off of a sign, visiting trees, bicycle racks, buildings, wetlands, and so on. Build the whole activity into a fun and educational cohesive theme. I have some samples of geocaching courses with themes of historical transportation, the Revolutionary War, aliens, and more, on these USGS Education web pages.

Examine Anton Ninno's Fun With GPS article on:

http://www.monitoringtimes.com/html/gps.pdf

Buy the ESRI Press book by Don Cooke entitled "Fun With GPS", that is full of these and other activities.

Load the ArcExplorer Java Edition for Education from ESRI on your laptops (or ArcGIS / ArcView or other GIS or mapping software) with an aerial and topo map of the neighborhood where you are conducting the activity. Then have the students upload the points they collect on the ground. You might have them WRITE their names on the ground with GPS waypoints (with 100 meter high letters, for example) and then upload them on top of the aerials/topos. Then in your GIS session, have a contest: Whose name is the most legible?

Go on a geocaching expedition! www.geocaching.com

Even more applicable to education, create and examine some Earthcaches.

Have a look at my Degree Confluence Project educational ideas - fascinating!

NYGPS -- A Community of Teachers Using GPS for Math, Science & Social Studies Instruction http://groups.yahoo.com/group/nygps/

What do I need to know to get my GPS into correct operation?

2009-04-29T05:52:00.000-05:00

What do I need to know to get my GPS into correct operation?

We generally emphasize the following four points:

a) Select a coordinate system. We usually suggest using either the Universal Transverse Mercator System (UTM) or latitude/longitude. Using UTM results in easier plotting on the USGS 7.5’ quadrangle maps. The coordinate system displayed by your GPS is usually just a position format selection on your unit’s navigation set up page.

b) Select the correct horizontal datum. Most GPS units default to a datum called the World Geodetic System of 1984 (WGS84). However, most USGS maps are referenced to a different datum, the North American Datum of 1927 (NAD27). A few USGS maps are set to the North American Datum of 1983 (NAD83), which is virtually identical to WGS84. Check the map information at the lower left corner of the USGS 7.5’ quadrangle to determine the correct datum used in the making of the map. Correct datum is especially important of you are using the UTM coordinate system. Your GPS setup menu may present several variations of NAD27 to select from; most users will select NAD27 CONUS, which is appropriate for the continental US.

c) Be aware that the vertical heights displayed by your recreational GPS receiver will not agree well with USGS map elevations. The main reasons for this discrepancy is the inherent poor fix geometry available for vertical determinations (the earth is always blocking some of the desired satellites) and the use of different reference surfaces for the vertical measurement. DO NOT USE GPS ELEVATIONS FOR CRITICAL NAVIGATION DECISIONS.

d) Select which “North” your GPS receiver will use as the zero degree reference. The default in your receiver is probably true north = 0 degrees. You can also select magnetic north = 0 degrees or grid north (north-south lines of the UTM grid) = 0 degrees. Many users select magnetic north as zero degrees to they can follow a compass bearing without converting the azimuth to true north. Many GPS units automatically calculate the local magnetic variation (declination) for the fix time and date.

How is LAAS different from WAAS?

2009-04-28T13:15:00.001-05:00

Like the Wide Area Augmentation System (WAAS), LAAS relies on GPS for basic navigation signals. However, with WAAS, GPS-corrected navigation signals come from space, broadcast from WAAS geostationary satellites. With LAAS, the GPS-corrected navigation signal is broadcast from a LAAS VHF data broadcast transmitter at or near the airport. Although LAAS and WAAS will operate independently, LAAS will complement WAAS by providing GNSS Landing System (GLS) landing service for Category II/III precision approach operations. LAAS will also provide GLS Category-I capability at locations where WAAS service may not be available. Other differences between WAAS and LAAS include the manner in which the availability of the systems are computed, the manner in which avionics receive information on approach procedures, and the vertical alert limits (VAL) associated with each system.

What is LAAS?

2009-04-28T13:14:00.001-05:00

The Local Area Augmentation System (LAAS) is a satellite navigation system being developed by the FAA. LAAS uses signals from the Global Positioning System (GPS) to develop an extremely accurate navigation signal that focuses its service on the airport area (approximately a 20-30 mile radius).

How does WAAS know that the correction it sends is valid to my particular location?

2009-04-27T12:07:00.001-05:00

The WAAS supplies two different sets of corrections: 1) corrected GPS parameters (position, clock, etc) and 2) Ionospheric parameters. The first set of corrections is user position independent - they apply to all users located within the WAAS service area. The second set of corrections is area specific. WAAS supplies correction parameters for a number of points (organized in a grid pattern) across the WAAS service area. The user receiver computes ionospheric corrections for the received GPS signals based on algorithms which use the appropriate grid points for where the user is located. Further, the appropriate grid points may differ for each GPS satellite received and process by the user receiver as the GPS satellites are located at various positions in the sky relative to the user. The combination of the two sets of corrections allows for significantly increased user position accuracy and confidence anywhere in the WAAS service area.

What is WAAS?

2009-04-27T12:06:00.001-05:00

The Wide Area Augmentation System (WAAS) uses a system of ground stations to provide necessary augmentations to the GPS SPS navigation signal. A network of precisely surveyed ground reference stations is strategically positioned across the country including Alaska, Hawaii, and Puerto Rico to collect GPS satellite data. Using this information, a message is developed to correct any signal errors. These correction messages are then broadcast through communication satellites to receivers onboard aircraft using the same frequency as GPS. The WAAS is designed to provide the additional accuracy, availability, and integrity necessary to enable users to rely on GPS for all phases of flight, from en route through GLS approach for all qualified airports within the WAAS coverage area. This will provide a capability for the development of more standardized precision approaches, missed approaches, and departure guidance for approximately 4,100 ends of runways and hundreds heliport/helipads in the NAS. WAAS will also provide the capability for increased accuracy in position reporting, allowing for more uniform and high-quality worldwide Air Traffic Management (ATM). In addition, WAAS will provide benefits beyond aviation to all modes of transportation, including maritime, highways, and railroads.

What is Differential GPS (DGPS)?

2009-04-26T13:15:00.003-05:00

DGPS achieves enhanced accuracy since the reference and user receivers both experience common errors that can be removed by the user. Position errors less than 10 meters are typically realized.

In the basic form of DGPS, the position of a reference receiver at a monitoring or reference station is surveyed in, that is, its position is known accurately. The user receiver should be no more than about 300 miles away from the reference receiver which makes pseudorange measurements, just as any user receiver would. However, because the reference receiver knows its position accurately, it can determine “biases” in its pseudorange measurements. For each satellite in view of the reference receiver, these biases are computed by differencing the pseudorange measurement and the satellite-to-reference receiver geometric range. These biases incurred in the pseudorange measurement process include errors arising from ionospheric delay, tropospheric delay, and satellite clock offset from GPS time. For real-time applications, the reference station transmits these biases, called differential corrections, to all users in the coverage area of the reference station. Users incorporate these corrections to improve the accuracy of their position solution.

For the basic local area DGPS (LADGPS) the position solutions of users further away from the reference station are less accurate than those closer to the monitoring station because pseudorange measurement errors tend to be spatially correlated. This loss of accuracy due to spatial decorrelation can be improved with more sophisticated techniques that fall under the heading of wide area DGPS (WADGPS) such as WAAS.

What augmentations to the basic GPS service is the FAA working on and why?

2009-04-26T13:15:00.001-05:00

The FAA is developing the Wide Area Augmentation System (WAAS) and the Local Area Augmentation System (LAAS). Both augmentation systems focus on the same concerns: integrity, availability, and accuracy.

Integrity is the ability to alert users, within a prescribed number of seconds (depending on the type of flight operation), when GPS should not be used for navigation. Availability is needed to assure users that the basic GPS civil service is accessible nearly 100% of the time. Accuracy enhancements are necessary to conduct precision approach and terminal navigation operations.

The WAAS will cover the Continental U.S. and provide a navigation signal capable of supporting navigation from enroute through Category I precision approach. LAAS will cover approximately a 30-mile radius and will provide up to a Category III precision approach. WAAS and LAAS will work together to provide users a navigation capability for all phases of flight.

Is the basic GPS signal sufficient to meet all the needs of civil aviation?

2009-04-26T13:14:00.001-05:00

This is not a simple yes/no answer. The answer is that it depends on the service requirements of each user or aviation authority. For many countries, GPS supplies a better capability than the existing ground-based systems or lack thereof. Yet for other countries with large infrastructures, the GPS signal does not meet the accuracy, integrity, availability, and continuity requirements critical to safety of flight. Enhancements to the Global Positioning System (GPS) such as the Wide Area Augmentation System (WAAS) and Local Area Augmentation System (LAAS) provide the necessary corrections for meeting safety-of-life flight requirements.

What concerns are there regarding Radio Frequency Interference (RFI)?

2009-04-24T15:32:00.002-05:00

As with all navigation aids, Radio Frequency Interference (RFI), unintentional or intentional, is always a concern. The FAA is evaluating several GPS interference detection systems, which will determine the direction and source of the GPS interference. The FAA is also working with DOD and other agencies to make sure that GPS augmentation systems detect and mitigate the effects of interference.

How vulnerable are GPS satellites to jamming and interference?

2009-04-24T15:32:00.001-05:00

GPS satellite signals, like any other navigation signals, are subject to some form of interference. The FAA is actively working with the U.S. Department of Defense and other U.S. Government Agencies to detect and mitigate these effects and make sure that the GPS and any related augmentation systems are available for safe aviation operations. As with all navigation aids, interference, whether intentional or unintentional, is always a concern. A number of methods for minimizing interference have been identified and tested and others are being investigated. The FAA is also working to make sure augmentation systems detect and mitigate these effects.

Are there plans to increase the capabilities of GPS?

2009-04-24T15:31:00.000-05:00

One of the main components of GPS modernization is the addition of two new navigation signals for civil use. These signals will be in addition to the existing civilian service broadcast at 1575.42 MHz (L1). The first of these new signals will be a new civil code, called L2C, which will be added on the existing L2 carrier, located at 1227.60 MHz. It will be available for general use in non-safety critical applications. The Block IIR-M satellite, the first to add his capability was launched September 25, 2005. A third civil signal, located at 1176.45 MHz (L5), will be provided initially on GPS Block IIF satellites beginning in 2007, and continuing with the Block III satellites scheduled for launch beginning in 2012. This new L5 signal is protected worldwide for aeronautical radionavigation use, and will support aviation safety-of-life applications. The addition of L5 will make GPS a more robust radionavigation service for many aviation applications, as well as all ground-based users (maritime, railways, surface, shipping, agriculture, recreation, etc.)

At the current GPS satellite replenishment rate, all three civil signals (L1-C/A, L2C, and L5) will be available for initial operational capability by 2012, and for full operational capability by approximately 2015.

How Can Civil Users Depend on a System Controlled by the U.S. Military?

2009-04-23T20:56:00.002-05:00

GPS is owned and operated by the U.S. Government as a national resource. DOD is the "steward" of GPS, and as such, is responsible to operate the system in accordance with the signal specification. The National Space-Based Positioning, Navigation, and Timing (PNT) Executive Committee was established by Presidential directive in 2004 to advise and coordinate federal departments and agencies on matters concerning the Global Positioning System (GPS) and related systems. This Committee replaced the Interagency GPS Executive Board (IGEB), which oversaw GPS policy matters from 1996 to 2004. The Executive Committee is chaired jointly by the Deputy Secretaries of Defense and Transportation. Its membership includes equivalent-level officials from the Departments of State, Commerce, and Homeland Security, the Joint Chiefs of Staff, and NASA. Components of the Executive Office of the President participate as observers to the Executive Committee, and the FCC Chairman participates as a liaison.

DOD is required by law to "maintain a Standard Positioning Service (SPS) (as defined in the Federal Radionavigation Plan and the Standard Positioning Service Signal Specification) that will be available on a continuous, worldwide basis," and, "develop measures to prevent hostile use of GPS and its augmentations without unduly disrupting or degrading civilian uses." These strict requirements and current augmentation systems should actually make DOD use of the system transparent to the civil user. (Note: There will, necessarily, be localized testing of the system by military and development teams but the testing will fall under strict notification guidelines of safety-of-life users such as Coast Guard and FAA).

U.S. transportation, public safety, economic, scientific, timing, and other users rely on GPS extensively. In aviation and maritime transportation, GPS is used for "safety of life" navigation and it is a critical system for these applications. DOD is the steward of the system, responsible to maintain the signal specification; the PNT provides management oversight to assure that civil and military needs are properly balanced.

What is Selective Availability (SA)?

2009-04-23T20:56:00.001-05:00

SA was a technique implemented by the DOD to intentionally degrade a user’s navigation solution. The single largest source of error for SPS users was SA. The net result of SA was about a five-fold increase in positioning error. DOD achieved signal degradation by altering (also known as dithering) the satellite clock. Another means designed by DOD to degrade GPS performance was to broadcast less accurate ephemeris parameters.

The DOD-authorized users were able to undo SA. However, due to the fact that SA is spatially correlated, civil users were able to eliminate SA through the implementation of Differential GPS (DGPS), albeit an additional expense on the part of the users.

What Are the Service Levels Provided by GPS?

2009-04-22T19:30:00.002-05:00

GPS provides two levels of service:

a Standard Positioning Service (SPS) for general civil use; and
a Precise Positioning Service (PPS) primarily intended for use by the Department of Defense and U.S. allies.

There are no restrictions on SPS usage and is available to users worldwide. With Selective Availability (SA) , SPS provides predictable accuracies of 100m (2drms, 95%) in the horizontal plane and 156m (95%) in the vertical plane. UTC (USNO) time dissemination accuracy is within 340 nanoseconds (95%) referenced to the time kept at the U.S. Naval Observatory. These accuracies reflect the last signal specification in the Federal Radio Navigation Plan which is in the process of being revised to reflect the accuracy obtained following the deactivation of Selective Availability. Without SA, SPS accuracy would be of the order of 25m (2 drms, 95%) in the horizontal plane and 43m (95%) in the vertical plane.

PPS provides a predictable accuracy of at least 22m (2drms, 95%) in the horizontal plane and 27.7m (95%) in the vertical plane. PPS provides UTC (USNO) time transfer accuracy within 200 nanoseconds (95%) referenced to the time kept at the U.S. Naval Observatory.

PPS is primarily intended for military and select government agency users. Civilian use is permitted but only upon special U.S. Department of Defense approval.

How Is GPS Used?

2009-04-22T19:30:00.001-05:00

GPS receivers collect signals from satellites in view. They display the user's position, velocity, and time, as needed for their marine, terrestrial, or aeronautical applications. Some display additional data, such as distance and bearing to selected waypoints or digital charts.

The GPS concept of operation is based upon satellite ranging. Users determine their position by measuring their distance from the group of satellites in space. The satellites act as precise reference points.

Each GPS satellite transmits an accurate position and time signal. The user's receiver measures the time delay for the signal to reach the receiver, which is the direct measure of the apparent range (called a "pseudorange") to the satellite. Measurements collected simultaneously from four satellites are processed to solve for the three dimensions of position (latitude, longitude, and altitude) and time. Position measurements are in the worldwide WGS-84 geodetic reference system, and time is with respect to a worldwide common U.S. Naval Observatory Time (USNO) reference.

What Is GPS?

2009-04-22T19:28:00.000-05:00

GPS consists of three segments - the satellite constellation, ground control network, and user equipment. The satellite constellation comprises satellites in low earth orbit that provide the ranging signals and navigation data messages to the user equipment. The ground control network tracks and maintains the satellite constellation by monitoring satellite health and signal integrity and maintaining the satellite orbital configuration. Furthermore, the ground control network also updates the satellite clock corrections and ephemerides as well as numerous other parameters essential to determining user position, velocity and time (PVT). The user equipment receives signals from the satellite constellation and computes user PVT. More details on each of the aforementioned GPS segments are provided below.

GPS Satellite Constellation:

The baseline satellite constellation consists of 24 satellites positioned in six earth-centered orbital planes with four operation satellites and a spare satellite slot in each orbital plane. The system can support a constellation of up to thirty satellites in orbit. The orbital period of a GPS satellite is one-half of a sidereal day or 11 hours 58 minutes. The orbits are nearly circular and equally spaced about the equator at a 60-degree separation with an inclination of 55 degrees relative to the equator. The orbital radius (i.e. distance from the center of mass of the earth to the satellite) is approximately 26,600 km.

With the baseline satellite constellation, users with a clear view of the sky have a minimum of four satellites in view. It’s more likely that a user would see six to eight satellites. The satellites broadcast ranging signals and navigation data allowing users to measure their pseudoranges in order to estimate their position, velocity and time, in a passive, listen-only mode.

Ground Control Network:

At the heart of the Ground Control Network is the Master Control Station (MCS) located at the Schriever (formerly named Falcon) Air Force Base near Colorado Springs , Colorado . The MCS operates the system and provides command and control functions for the satellite constellation.

The satellites in orbit are continuously tracked from six USAF monitor stations spread around the globe in longitude: Ascension Island , Diego Garcia, Kwajalein , Hawaii , Cape Canaveral and Colorado Springs . The monitor stations form the data collection component of the control network. A monitor station continuously makes pseudorange measurements to each satellite in view. There are two cesium clocks referenced to GPS system time in each monitor station. Pseudorange measurements made to each satellite in view by the monitor station receiver are used to update the master control station’s precise estimate of each satellite’s position in orbit.

User Equipment:

The user equipment, often referred to as “GPS receivers”, captures and processes L-band signals from the satellites in view for the computation of user position, velocity and time.

Wide Area Augmentation System - Program Structure

2009-04-20T22:37:00.001-05:00

Wide Area Augmentation System - Program Structure

To develop and field a system as complex as the Wide Area Augmentation System, there are a variety of underlying supporting activities.

The WAAS program consists of several functional areas:

WAAS Research and Development - Focuses on ionospheric issues, antenna development to mitigate multi-path, Alaska connectivity, and the support of the WAAS Integrity and Performance Panel (WIPP). The National Satellite Test Bed (NSTB) enables a major part of R&D work.
WAAS System Engineering -Provide oversight of the WAAS prime contractor's work to ensure that all aspects of the system engineering discipline are being met.
WAAS System Architecture - Review and monitor the overall WAAS concept to ensure that WAAS is being properly implemented.
WAAS Software Engineering - Review CDRLs and software-related contract deliverables from the prime contractor (Raytheon) to ensure appropriate S/W development procedures are being followed, including RTCA DO-178B.
WAAS WIPP Support - Guide development of S/W integrity monitors for WAAS. Co-chaired by FAA and Stanford University.
WAAS Test and Evaluation - Ensure that WAAS testing is adequate and complete.
WAAS System Security - Ensure entities without proper authorization cannot utilize or compromise the WAAS.
WAAS Transition and Field Support - Ensure all supporting efforts are completed to move WAAS from R&D, through acquisition, and into an operational system.
WAAS GEO SAT Acquisition - Ensure the adequate number of geostationary satellites to provide required coverage and availability.
WAAS Process Improvement/integrated Capability Maturity Model - enhance processes and continuous improvement of these processes related to the WAAS program.
WAAS Risk Management - Identify, analyze categorize, mitigate, and track WAAS-related risks.
WAAS Configuration Management - Ensure all WAAS components, both hardware and software, are managed and maintained in an appropriate manner and in accordance to FAA requirements.
WAAS Contracts/Finance - Manage the prime contractor's cost, schedule, and performance; and review all deliverables.
WAAS Business Management - Support and manage the WAAS budget process.
WAAS Planning/Program Documentation - Develop and maintain strategic planning documents and Acquisition Management System (AMS) documents required by the AMS process.

The FAA WAAS Project Team is responsible for the development and acquisition of the WAAS; however, to ensure a smooth and successful transition of the WAAS into the FAA's other lines of business and into the National Airspace System, there are several other FAA organizations involved in the development and acquisition of the WAAS.

These other FAA organizations include:

ASU-240 (FAA Quality Assurance Division) - These are FAA personnel located on-site at Raytheon Corporation to ensure that Raytheon's products meets their quality and reliability contractual obligations to the FAA.
AOP-1000 (FAA NAS In-Service Management) - These are FAA personnel who support the Deployment Planning Process, Standard Operating Procedures, and WAAS Operations and Maintenance Plan.
ASU-200 (FAA Quality Assurance Division) - These are FAA personnel who provide part-time support onsite at Raytheon Corporation to review software development activities.
AND-720 (FAA Navigation Systems Implementation) - These are FAA personnel who support fielding activities, such as the commissioning and deployment planning process involved in the Transition and Field Support portion of the WAAS project.
AND-702 (FAA Navigation Systems Engineering) - These are the FAA personnel who provide policy oversight on system engineering functions, such as security, configuration management, GPS Modernization, and participation in the Interagency GPS Executive Board (IGEB).
AOS-240 (FAA National Airways Systems Engineering Division Operational Support Directorate) - These are the FAA personnel located at the FAA Mike Monroney Aeronautical Center in Oklahoma City, Oklahoma, and represent the concerns of system maintainers once the system is fielded. Support activities include software support activity, OT&E shakedown, technical instruction books (TIB), ESTS Tools, maintenance technical handbooks, and operational CM, and safety assurance.
AIR-130 (FAA Aircraft Certification Service) - These are FAA headquarter personnel who set requirements based on FAA certification criteria to ensure the WAAS is safe to use by aircraft operating in the National Airspace System. Support activities include requirements documentation, safety assurance, and RTCA and GNSSP support.
AFS-430 (FAA Flight Technologies Requirements) - This branch represents the pilot/user community.

Wide Area Augmentation System - Benefits

2009-04-20T22:35:00.000-05:00

Wide Area Augmentation System - Benefits

The WAAS will allow GPS to be used as a primary means of navigation from takeoff through Category I precision approach. Other modes of transportation also benefit from the increased accuracy, availability, and integrity that WAAS delivers. The WAAS broadcast message improves GPS signal accuracy from 100 meters to approximately 7 meters.

The benefits of WAAS to civil aviation will be substantial. WAAS improves the efficiency of aviation operations due to:

Greater runway capability
Reduced separation standards which allow increased capacity in a given airspace without increased risk
More direct enroute flight paths.
New precision approach services
Reduced and simplified equipment on board aircraft
Significant government cost savings due to the elimination of maintenance costs associated with older, more expensive ground-based navigation aids (to include NDBs, VORs, DMEs, and most Category 1 ILSs)

Wide Area Augmentation System - How it Works

2009-04-19T18:08:00.001-05:00

Unlike traditional ground-based navigation aids, the WAAS covers nearly all of the National Airspace System (NAS). The WAAS provides augmentation information to GPS receivers to enhance the accuracy and reliability of position estimates.

The signals from GPS satellites are received across the NAS at many widely-spaced Wide Area Reference Stations (WRS) sites. The WRS locations are precisely surveyed so that any errors in the received GPS signals can be detected.

The GPS information collected by the WRS sites is forwarded to the WAAS Master Station (WMS) via a terrestrial communications network. At the WMS, the WAAS augmentation messages are generated. These messages contain information that allows GPS receivers to remove errors in the GPS signal, allowing for a significant increase in location accuracy and reliability.

The augmentation messages are sent from the WMS to uplink stations to be transmitted to navigation payloads on Geostationary communications satellites.

The navigation payloads broadcast the augmentation messages on a GPS-like signal. The GPS/WAAS receiver processes the WAAS augmentation message as part of estimating position. The GPS-like signal from the navigation transponder can also be used by the receiver as an additional source for calculation of the user’s position.

WAAS also provides indications to GPS/WAAS receivers of where the GPS system is unusable due to system errors or other effects. Further, the WAAS system was designed to the strictest of safety standards – users are notified within six seconds of any issuance of hazardously misleading information that would cause an error in the GPS position estimate.

Wide Area Augmentation System (WAAS)

2009-04-19T18:07:00.000-05:00

WAAS is an extremely accurate navigation system developed for civil aviation. Before WAAS, the U.S. National Airspace System (NAS) did not have the potential to provide horizontal and vertical navigation for approach operations for all users at all locations. With WAAS, this capability is a reality.

WAAS provides service for all classes of aircraft in all phases of flight - including en route navigation, airport departures, and airport arrivals. This includes vertically-guided landing approaches in instrument meteorological conditions at all qualified locations throughout the NAS.