Abstract: The invention presented in this disclosure gives methods to estimate and compensate for the multi-path in a typical navigational or spread spectrum receiver. The multi-path delay is estimated based on the outputs of different correlators of the receiver. Unlike three correlators normally used, the present disclosure uses five correlators, namely, Early2 (E2), Early1 (E1), Prompt (P), Late1 (L1) and Late2 (L2). The possible multi-path scenarios are classified into six different cases depending upon the reflected signal delay and the errors are computed. Further, the algorithm in the present disclosure can be extended to any correlators spacing.

Abstract: The present invention is related to location positioning systems, and more particularly, to a method and apparatus for providing reliable extended ephemeris information and indicators of quality. According to one aspect, the invention employs a concept of Approximate Accuracy Symmetry, in which a history of broadcast ephemerides is logged for each satellite, and used as a reference to evaluate the potential accuracy of the predicted orbit for each satellite in the future. According to further aspects, the desired accuracy information for the extended ephemerides can be reliably provided in advance.