How To Program A Garmin Gps
WAAS-enabled GPS System
Jeff Sanders
Garmin GPS Navigation Systems
www.GpsFrontier.com
05/04/1909
WAAS-enabled GPS System
WAAS (Wide Area Augmentation System) was developed by Federal Aviation Administration to increase the global positioning system to improve its accuracy, integrity and availability. WAAS was originally intended to allow to aircraft that rely on GPS for all phases of flight, including precision approach to the airport within its coverage area. The WAAS system typically provides better than 1.0 meters to 1.5 meters laterally and vertically along most of the contiguous United States and large parts of Canada and Alaska. This accuracy can of provideing aircraft with the precision necessary for safety and navigational approaches on board for all weather conditions. Information integrity is WAAS no more than 3 seconds per year erroneous data that allows the system to be considered safe by the FAA for instrument flight rules.
Although originally developed for aviation, WAAS is not limited only to the aviation industry, any GPS receiver that is capable of receiving the WAAS signal may benefit from she correction data, which makes GPS positioning more precise. In fact a WAAS-enabled GPS receiver can even give instructions to your car lane traveling (as long as the mapping program supports the "Lane Assist" directions). Because the Wide Area Augmentation System is rapidly becoming standard in the GPS industry, most new GPS receivers are now compatible with WAAS. As with the conventinal GPS, WAAS system does not come with any additional cost or use fees. All that is required is that the WAAS-enabled GPS receiver so you can receive and decode the data and then be able to apply corrections to your position. Currently the WAAS service is limited to the U.S., Canada, Alaska and Hawaii. Although independent of WAAS, Europe and Asia are working on their own systems of correction Additional GPS. Europe has the Euro Geostationary Navigation Overlay Service (EGNOS) and Japan is working on its "Multi-functional satellite Augmentation System (MSAS).
How WAAS Works
WAAS uses a network of approximately 25 ground-based wide-area Reference Stations (WRS) in North America and Hawaii, to measure small variations in the GPS satellite signals in the hemisphere Western. These ground stations surveyed precisely monitor and collect information on the GPS signals and send their data to the three Wide Area Master Stations (WMS). The WMS generates two different sets of corrections: fast and slow. The quick fixes are the mistakes that are changing rapidly and have an interest paramount to the GPS satellite positions instantly and clock errors. These corrections are independent user's position, which means you can apply instantly by any receiver in WAAS broadcasting area. The corrections are slow to the estimates of long-term error ephemeric and the clock and ionospheric delay information.
Once these corrections are generated, the master stations are sent to two pairs of stations, uplink earth (GUS) that transmit correction messages a series of geostationary satellites that transmit correction data to Earth. Then, WAAS-enabled GPS receivers use this information to make signial corrections to the original GPS, WAAS-enabled receiver providing a more accurate GPS. GPS receiver uses the transmission of information from each GPS satellite to determine their location and current time. Depending on the GPS device, a GPS receiver only needs to receive a signal from 3-4 satellites (of the 31 satellites currently transmitting a signal for civilian users) to calculate its position. In addition to the GPS signal, WAAS GPS receiver can also receive geostationary WAAS signal satellites.
The two types of messages WAAS correction (fast and slow) are used by the GPS in different ways. The type of correction quick correction data includes data from the satellite position and clock to determine your current location using GPS calculations normal. Once a approximate position fix is obtained by the GPS receiver begins to use the slow corrections to improve accuracy. Slow correction of data includes ionospheric delay. When GPS signal travels from the satellite to the receiver, which passes through the ionosphere. The receiver calculates the location where the signal crossed the ionosphere and, if you received ionospheric delay value for that location, correct the error that the ionosphere created. Unlike the data fast, the slow data need not be updated frequently due to ionospheric conditions do not change quickly. While the data can be slow refresh every minute if necessary, are only updated every two minutes and are considered valid for up to six minutes.
WAAS System Limitations
(1) WAAS is currently available only for the United States and much of Canada and Alaska, but there are plans to expand into other countries and continents (2). Because WAAS broadcasting satellites are geostationary causes less than 10 degrees above the horizon for locations north of 71.4 ° latitude. This means that aircraft in areas of Alaska or northern Canada may have difficulty maintaining a lock on the WAAS signal. (3) For the calculation of ionosphere is a delay grid point, that point should be located between a satellite and a reference station. The low number of satellites and ground stations limit the number of points that can be calculated. (4) aircraft conducting WAAS approaches must have certified GPS receivers.
Jeff Sanders
Garmin GPS Navigation Systems
www.GpsFrontier.com
05/04/1909
About the Author
With a passion for GPS systems, as well as all electronic devices and a curious nature to find out how they work, I was taking things apart and putting them back together again at an early age.
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