1. An SPS system for identifying the location of a receiver in the presence of satellite signal attenuation comprising: a plurality of orbital satellites sending synchronized encoded signals on a carrier frequency wherein said encoded signals have repeated epochs containing synchronization data; a receiver for detecting, acquiring, tracking a set of the encoded signals and simultaneously determining the code phases of said set with respect to said epochs; an aiding source to transmit information to the SPS system, and; a processor executing an algorithm for computing an initial approximate location from measured satellite Doppler differences.