Here are some selected sources for GPS data concepts:
Starting point for Android GPS development using the location SDK libraries
Interestingly enough, the link above provides the following warning:
“This API is not the recommended method for accessing Android location”
However, it is important to remember that this is only Google’s view. Using the android.location is the most basic way to develop GPS applications without having to rely on any external sources of Geo data. The app GpsIsUp referenced below is an example of an application that uses android.location exclusively without the need to use Google specifics which likely involve their only geographic data (i.e. Google Maps and the like).
AOSP Source code for the Location GPS code in Froyo
GPSIsUp, an open source Android application useful for learning the basics of satellite display and diagnostics
A description of open source Android applications that do not use Google proprietary data.
This API is not the recommended method for accessing Android location