Garmin GPSMAP 296 What is WAAS, Using, Wiring, Signal, Tuning, Beacon, Beacon, No Beacon, Check Beacon, Differential, Scanning for

APPENDIX > LEARNING ABOUT GPS

•Check Beacon Wiring—the DGPS setting is enabled in the Interface sub tab on the Main Menu but no DGPS device is detected.

•No Beacon Signal—DGPS receiver is attached, but not transmitting RTCM data to GPS.

•Tuning Beacon—the receiver is tuning manually to a DGPS frequency.

•Using Differential—the unit is receiving DGPS corrections.

•Scanning for Beacon—the DGPS receiver is scanning for an available frequency.

What is WAAS?

The Wide Area Augmentation System (WAAS) is an FAA-funded project to improve the overall integrity of the GPS signal and increase location accuracy for users in North America.

The system is made up of satellites and approximately 25 ground reference stations located 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 data correction message.

According to the FAA’s Web site, testing of WAAS in September 2002 confirmed an accuracy performance of 1–2 meters horizontal and 2–3 meters vertical throughout the majority of the continental United States and portions of Alaska.

WAAS is just one service provider that adheres to the MOPS (Minimum Operational Performance Standard) for global Satellite Based Augmentation Systems (SBAS). Eventually, there will

be several services of worldwide geostationary communication satellites and ground reference stations.

All SBAS systems use the same receiver frequency; therefore, any operational SBAS system should be capable of providing your GPS unit with increased accuracy at any location in the world.

Currently, enabling WAAS on your Garmin GPSMAP 296 in regions that are not supported by ground stations may not improve accuracy, even when receiving signals from an SBAS satellite. In fact it can degrade the accuracy to less than that provided by GPS satellites alone. For this reason, when you enable WAAS on your Garmin GPS receiver, the receiver automatically uses the method that achieves the best accuracy. To enable WAAS, refer to page 6.

For more information, go to http://gps.faa.gov/Programs/WAAS/waas.htm.

GPSMAP 296 Pilot’s Guide 139