wide-area augmentation system

Wide-Area Augmentation System

[¦wīd ¦er·ē·ə ȯg·mən′tā·shən ‚sis·təm]
A satellite-based augmentation system developed by the Federal Aviation Administration in the United States. Abbreviated WAAS.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

wide-area augmentation system (WAAS)

wide-area augmentation system (WAAS)click for a larger image
The WAAS is a satellite navigation system consisting of the equipment and software that augment the GPS (global positioning system) Standard Positioning Service (SPS). The WAAS provides enhanced integrity, accuracy, availability, and continuity over and above the GPS and the SPS. The differential correction function provides the improved accuracy required for precision approaches. This augmentation of the GPS system will permit its use as a primary means of navigation for en route travel, non-precision approaches, and CAT I approach capability at some airports.
WAAS is based on a network of approximately 35 ground reference stations located in the Continental United States. Each of these reference receivers is precisely surveyed, enabling each to determine any error in the GPS signal being received at the station. The error is then fed to the master station computer which calculates correction algorithms and assess the integrity of the entire GPS system. The data is then up linked to a communication satellite in a geostationary orbit. This communication satellite forwards the correction signal to the aircraft's GPS receiver. The aircraft receiver then makes necessary adjustments to provide improved positioning accuracy. The communication satellites also act as GPS navigation satellites, thus adding to the number of satellites in the GPS constellation.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved
References in periodicals archive ?
Two, differential GPS (DGPS) and wide-area augmentation system (WAAS), are already being used in some available commercial GPS navigation systems.
Satmex's commissioning of a payload from Boeing follows the agreement it has concluded with Raytheon for a Wide-Area Augmentation System (WAAS) payload that will enhance the availability and accuracy of Global Positioning System (GPS) signals for the FAA.
The self-contained unit uses the Wide-Area Augmentation System to deferentially correct the GPS signal on board with horizontal errors less than 3 m (10 ft).
The Wide-Area Augmentation System (WAAS) approaches we have now are capable of replacing Cat-I ILSs with DAs as low as 200 feet above the threshold.