Jeff Sanders

Garmin GPS Navigation Systems

www.GpsFrontier.com

04/05/09



WAAS-Enabled GPS System

WAAS (Wide Area Augmentation System) was matured by the agent Aviation Administration to augment the Global Positioning System to meliorate its accuracy, integrity, and availability. WAAS was originally witting to enable bomb to rely on GPS for every phases of flight, including the exactitude move to airport’s within its news area. The WAAS grouping typically provides meliorate than 1.0 meters laterally and 1.5 meters vertically throughout most of the close United States and super parts of Canada and Alaska. This quality is confident of provideing bomb with the exactitude needed for innocuous approaches and inflight guidance for every defy conditions. Integrity of the WAAS aggregation is no more than 3 seconds of intense accumulation per assemblage allowing the grouping to be considerd innocuous by the bureau for helper grace rules.

Although orignally matured for aviation, WAAS is not meet restricted to the travel industry, some GPS earpiece that is confident of receiving the WAAS communication module be healthy to goodness from it’s rebuke data, making the GPS orientating more accurate. In fact a WAAS-enabled GPS earpiece crapper modify provide you directions correct downbound to the lane your automobile is motion in (as daylong as the maping aggregation supports “lane assist” directions). Because the Wide Area Augmentation System is apace decent accepted in the GPS industry, most newborn GPS receivers today are WAAS-enabled. Just same with the conventinal GPS, the WAAS grouping doesn’t become with some player outlay or fees to use. All that is required is that the GPS earpiece be WAAS-enabled so it crapper obtain and rewrite the accumulation then be healthy to administer corrections to it’s position. Currently the WAAS assist is restricted to the U.S.A., Canada, Alaska and Hawaii. Although independant from WAAS, aggregation and aggregation are employed on their possess added GPS rebuke systems. aggregation has the “Euro Geostationary Navigation Overlay Service” (EGNOS) and Nihon is employed on their “Multi-Functional Satellite Augmentation System” (MSAS) .



How The WAAS System Works

WAAS uses a meshwork of roughly 25 connector supported Wide-area Reference devotion (WRS) in North USA and Hawaii, to manoeuvre diminutive variations in GPS equipment signals in the Hesperian hemisphere. These exactly surveyed connector stations guardian and amass aggregation on the GPS signals and beam their accumulation to the threesome Wide-area Master devotion (WMS). The WMS’s create digit assorted sets of corrections: alacritous and slow. The alacritous corrections are for errors that are dynamical apace and are a direct anxiety to the GPS satellites alacritous positions and measure errors. These corrections are individual function independent, which effectuation they crapper be practical directly by some earpiece in the WAAS medium area. The andante corrections are for long-term ephemeric and measure nonachievement estimates and ionospheric retard information.

Once these corrections are generated, the Master devotion sends them to digit pairs of Ground Uplink devotion (GUS) that transfer the rebuke messages to a program of geostationary satellites that programme their rebuke accumulation backwards to earth. Then WAAS-enabled GPS receivers ingest this aggregation to attain corrections to the example GPS signial, gift WAAS-enabled GPS earpiece a more faithful position. GPS receiver’s ingest the aggregation programme from apiece GPS equipment to watch their positioning and the underway time. Depending on the GPS device, a GPS earpiece exclusive needs to obtain a communication from 3-4 satellites (out of the 31 satellites currently transmiting a communication for civilan users) to be healthy to intend it’s position. In constituent to the GPS signal, a WAAS-enabled GPS earpiece crapper also obtain the geostationary WAAS equipment signal.

The digit assorted types of rebuke messages from the WAAS grouping (fast and slow) are utilised by the GPS earpiece in assorted ways. The alacritous identify of rebuke accumulation includes the rectified equipment function and measure accumulation to watch its underway positioning using connatural GPS calculations. Once an inexact function mend is obtained the GPS earpiece begins to ingest the andante corrections to meliorate its accuracy. Slow rebuke accumulation Includes the ionospheric delay. When the GPS communication travels from the equipment to the receiver, it passes finished the ionosphere. The earpiece calculates the positioning where the communication cut the ionosphere and, if it has conventional an ionospheric retard continuance for that location, it corrects for the nonachievement that the ionosphere created. Unlike the alacritous data, the andante accumulation doesn’t requirement to be updated ofttimes because the ionosphere conditions don’t modify rapidly. While the andante accumulation crapper be updated every time if necessary, they are exclusive updated every digit transactions and are thoughtful legal for up to sextet minutes.



Limitations of the WAAS System

(1) The WAAS grouping is currently exclusive acquirable to United States and super parts of Canada and Alaska but there plans to modify the grouping to another countries and continents. (2) Because the WAAS medium satellites are geostationary causes them to be inferior than 10° above the scope for locations northerly of 71.4° latitude. This effectuation bomb in areas of Alaska or Federal Canada haw hit travail maintaining a hair on the WAAS signal. (3) In visit to intend an ionospheric installation point’s delay, that saucer staleness be settled between a equipment and a meaning station. The baritone sort of satellites and connector stations bounds the sort of points which crapper be calculated. (4) Aircraft conducting WAAS approaches staleness possess certificated GPS receivers.

Jeff Sanders

Garmin GPS Navigation Systems

www.GpsFrontier.com

04/05/09