_GPSSELMODE returns the GPS selection mode as an integer.
0 = Autonomous.
1 = DGPS.
2 = Estimated (dead reckoned).
3 = Manual input.
4 = Simulator.
5 = Data not valid.
The GPS internal variables require a GPS (internal or external) that supports the Windows Sensor Location APIs. Note that your GPS may not support all of the variables. If a value is not supported Windows will return "Element not found". Unless otherwise specified, the values returned are decimal numbers (for example, 38.735122).