I was blown away when I saw (via Make)that someone had created a home-made GPS receiver.  Andrew Holme just may be a genius. He built an incredible four-channel GPS receiver using some repurposed FPGA board from a previous frequency synthesizer project. Then, by connecting it to a PC running a console app, Andrew’s receiver is now capable of tracking at least four satellites simultaneously, which is good enough to capture lat, long, and altitude.  This homemade GPS receiver should not be confused with the ultra-cool Poor mans GPS.  Read about the whole process here and be amazed.

 
Solutions are computed in earth-centred, earth-fixed (ECEF) coordinates. User location is converted to latitude, longitude and altitude with a correction for eccentricity of the earth, which bulges at the equator. (Make)