Noise shaping, sigma-delta, and how GPS is even possible

[alexwhittemore]

I have a slightly-better-than-basic idea of how noise shaping works, specifically in relation to sigma-delta converters, but I could use a clearer, dummy-version refresher. Especially I'm curious about noise as it relates to GPS, where the noise power is actually higher than the signal. Does GPS receiving even use the same kind of noise shaping to achieve the goal? How does it actually work? I know this would be valuable to me, and I'm guessing most others, especially hobbyists but probably a good number of pros, aren't particularly familiar either.