With four or more satellites, you get a 3-D fix that also gives your current elevation. The Earthmate has a 12-channel receiver to monitor up to 12 satellites simultaneously. The more satellites the GPS can lock onto, the more accurate your position information will be. Accuracy is a problem for any civilian GPS receiver because of selective availability, the purposeful degradation of the satellite signal by the Defense Department. Because civilian GPS signals are purposely degraded, positioning is only accurate to within at least 328 feet horizontally and 512 feet vertically.
Military receivers use the same satellites, but different radio signals and receivers.
The first time you initialize the Earthmate, it may take as much as 15 minutes, as the GPS must download a current almanac of satellites and their positions. Making sure you have an accurate system clock or that you can at least enter the current time will help in your GPS accuracy and the ease with which it finds satellites. The Street Atlas USA software works well with the Earthmate GPS, providing a track of where you are and in what direction you are moving. The interface is easy to use, and the ability to set up travel routes is extensive, flexible and robust. With a planned route, a notebook with speakers and your GPS receiver, Street Atlas can even give you audio driving directions.