THE TRANSITION TO ADS-B has been underway for well more than a decade now, yet questions abound. Automatic Dependent Surveillance-Broadcast forms the backbone of the FAA's next generation air transportation system. No longer will controllers be entirely reliant on ground-based radar to manage air traffic. Instead, aircraft will broadcast their positions to ATC and to each other. In order to provide the most accurate position information practical, the FAA insists that aircraft have a GPS receiver that incorporates a WAAS correction factor.The Wide Area Augmentation System itself is a marvel of engineering. Thirty-eight reference stations around the country, plus two masters and a backup, sit on precisely measured sites. Sensors there know exactly where they are, and they compare that position to the ones they receive from the constellation of GPS satellites-then account for small errors that may result from atmospheric or other interference. The ground stations send the corrected information to the master stations, which send the corrections up to three geostationary satellites. Those satellites broadcast the corrections on a frequency near the one used by the GPS satellites themselves. Your WAAS-enabled receiver uses the correction factor to further refine your position information, providing a more precise position than the raw GPS signal.
展开▼
