A. GARMIN GPS units have a potential position accuracy of 15 meters.

This is the same accuracy available in all commercially available GPS receivers.

The accuracy of the GPS units is not only dependent upon the GPS receiver design, but also by the U.S. DOD Selective Availability program (SA). Selective Availability, also known as SA, is a program that allows the U.S. DOD to degrade the accuracy of non-military GPS system by as much as +/- 100 meters. At the present time, the accuracy of all commercial GPS receivers can vary Between 15 to 100 meters depending on the level of degradation being imposed by the U.S. DOD.

Another factor that will effect the accuracy of the GPS receiver is the geometry of the satellites in view to the GPS receiver. A poor geometry situation can provide less accurate position readings, and this especially applies to GPS altitude measurements.

The altitude reading on the GPS unit can vary by +/- 450 ft. depending on the level of degradation being imposed under SA. It is not uncommon to see the altitude continuously drift up and down when SA is being imposed.