The Navy Navigation Satellite System (NNSS) is over fifteen years old and has well established its utility in position determination, from the knowledge of the satellite ephemeris and the observations of the Doppler shifts at the receiver.nThe satellite ephemeris is available in two forms. The broadcast ephemeris which can be received on real time basis is predictive and has larger uncertainties than the post fitted precise ephemeris whose availability is restrictive.nThis study is an effort to improve station position recovery using broad cast ephemeris in Doppler data reduction.
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