A GPS receiver system determines the presence of trackable signals at code
delays less than the prompt delay being tracked for a particular, signal
and changes the prompt delay to correspond to the smallest code delay
having a trackable signal. Trackable signals at large code delays are
multipath signals and may be separately tracked to aid in dead reckoning.
The trackable signals at code delays not adjacent to the current tracked
prompt delay may be tracked in the same channel as the prompt delay so
that all satellite channels are continuously evaluated for multipath
signals being tracked or a non-satellite specific channel may be used to
sequentially step through the satellite signals to evaluate multipath on
a satellite by satellite basis.