What is WAAS?
WAAS or Wide Area Augmentation System is a system of satellites and ground stations that work with GPS to improve the quality of signals and rectify errors. The quality of the signals can be up to five times better with WAAS. A GPS receiver with WAAS can give a position accuracy of within three meters. Further, WAAS does not need additional equipment or service fees.
The WAAS system has been developed by the Federal Aviation Administration (FAA) and the Department of Transportation (DOT) jointly for use in precision flight approaches. GPS alone is not sufficient to meet the accuracy levels FAA requires. WAAS was therefore developed to account for signal errors due to ionosphere disturbances, time errors, and satellite orbit errors. WAAS is also vital in getting information about the health of each satellite in the GPS network.
How WAAS Works
The WAAS system is made up of about 25 ground stations across the United States, that act as reference points to monitor the GPS satellite data. Of these 25 stations two stations, located on the East and West coasts respectively, gather data from the other stations and create the correction message. The correction takes into account the clock and orbit errors as well as delays caused by atmospheric disturbances. The corrected message then goes to a geostationary satellite (geostationary satellites are satellites with a fixed position over the equator) which then relays it to GPS receivers. These signals can be read by all WAAS enabled GPS receiver.
Who Benefits from It
The WAAS coverage is currently confined to North America. Further areas with tall trees and mountains may not be able to receive the WAAS signals. WAAS signals are easy to receive for open land and marine applications. An advantage WAAS has over differential GPS system is that WAAS gives coverage both inland and offshore whereas DGPS is entirely land-based. Further, unlike DGPS, WAAS does not need additional receiving equipment.