One of the main pieces of an Automatic Packet Reporting System is the ability for the station to determine it's location automatically. This is the job of the Global Positioning System Receiver. The GPS uses signals from a constellation of GPS satellites which are constantly orbiting the globe. Using sophisticated timing routines, it is possible to determine a three dimensional position fix based on radio signals received by the GPSr.
The position fix calculated by the GPSr is passed on to the program as a latitude, longitude, altitude, along with some other information such as course and speed. All of this information is used by the program to determine where it is located, and what maps to display on screen. This information is also used by the Genius routine to determine when it is necessary to send out an updated location report to the APRS network.
There are a number of screen elements that contain information from the GPS unit.
GPS Satellite Signal Level
Color code from Red meaning no signal through yellow to Green meaning good signal
Number of Satellites
The number of satellites that the receiver believes it should be able to see at the bottom, and the Number of satellites used in the solution on top of that
GPS Fix Type
This display has 4 options No Fix Not enough satellites in view for a solution. 2D Enough satellites for an aproximate location 3D Enough Satellites for an accurate location and altitude. 3D(D) Differential calculation for more accurate location
The direction you are moving in
Your speed in the unit format selected
Time in UTC