[tinfever]

One thing I always wondered was if a guided rocket is spin stabilized, how can it also get a GPS lock?

I expect either GPS guided rockets don't spin, or there is non-spinning part of the rocket that allows a GPS antenna to always point up.

Even inertial guidance would sound difficult with a spinning rocket, although I guess if you know exactly your rotational position relative to the earth, you could still calculate out how much you've moved up/down/left/right.

[programmer_dude]

Couldn't you use multiple antennas and switch to the antenna which is "up" depending on your orientation?