What is WAAS:
You've heard the term WAAS, seen it on packaging and ads for Garmin® products, and maybe even
know it stands for Wide Area Augmentation System. Okay, so what the heck is it? Basically, it's a system
of satellites and ground stations that provide GPS signal corrections, giving you even better position
accuracy. How much better? Try an average of up to five times better. A WAAS‐capable receiver can give
you a position accuracy of better than three meters 95 percent of the time. And you don't have to
purchase additional receiving equipment or pay service fees to utilize WAAS.
The origins of WAAS
The Federal Aviation Administration (FAA) and the Department of Transportation (DOT) are developing
the WAAS program for use in precision flight approaches. Currently, GPS alone does not meet the FAA's
navigation requirements for accuracy, integrity, and availability. WAAS corrects for GPS signal errors
caused by ionospheric disturbances, timing, and satellite orbit errors, and it provides vital integrity
information regarding the health of each GPS satellite.
How it Works
WAAS consists of approximately 25 ground reference stations positioned across the United States that
monitor GPS satellite data. Two master stations, located on either coast, collect data from the reference
stations and create a GPS correction message. This correction accounts for GPS satellite orbit and clock
drift plus signal delays caused by the atmosphere and ionosphere. The corrected differential message is
then broadcast through one of two geostationary satellites, or satellites with a fixed position over the
equator. The information is compatible with the basic GPS signal structure, which means any WAAS‐
enabled GPS receiver can read the signal.
Who benefits from WAAS?
Currently, WAAS satellite coverage is only available in North America. There are no ground reference
stations in South America, so even though GPS users there can receive WAAS, the signal has not been
corrected and thus would not improve the accuracy of their unit. For some users in the U.S., the position
of the satellites over the equator makes it difficult to receive the signals when trees or mountains
obstruct the view of the horizon. WAAS signal reception is ideal for open land and marine applications.
WAAS provides extended coverage both inland and offshore compared to the land‐based DGPS
(differential GPS) system. Another benefit of WAAS is that it does not require additional receiving
equipment, while DGPS does.
It just keeps getting better
http://www.garmin.com/aboutGPS/waas.html
Matthew Kimball – Retail Sales Trainer - Simulation Exercise
Garmin C330 FG (PANEL)v1.0
Personal Navigation System: Garmin C330
•
100 meters: Accuracy of the original GPS system,
which was subject to accuracy degradation
under the government‐imposed Selective
Availability (SA) program.
•
15 meters: Typical GPS position accuracy
without SA.
•
3‐5 meters: Typical differential GPS (DGPS)
position accuracy.
•
< 3 meters: Typical WAAS position accuracy.
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