Andrew Holme built this incredible four-channel GPS receiver using a repurposed FPGA board from a previous frequency synthesizer project. Connected to a PC running a console app, Andrew’s receiver is capable of tracking four satellites simultaneously, which is good enough to capture lat, long, and altitude. [via YC]
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.