Armed and Dangerous » Blog Archive » Why GPSes suck, and what to do about it
http://esr.ibiblio.org/?p=801

Why the NMEA standard is so much trouble

Away back in the dark and backward abysm of time when GPS technology was first being made generally available (e.g., 1993), only military-grade receivers were sensitive enough to use it where there were things like buildings and trees partly blocking the sky view. The first civilian customers to actually find a use for it were people messing about in boats. Thus it came to pass that the manufacturers of marine navigation systems were the first civilians to grapple with the question of how a GPS receiver should report TPV information over a wire to a navigational computer.