A Novel Ephemeris Extension Compaction/Decompaction Method

Lionel Garin, SaiPradeep Venkatraman, and Pramod Gupta

Abstract:	Nemerix’s NEXTM is a way to compute a GPS position with no instantaneous access to Satellite Broadcast Ephemeris. The principle is to predict in advance the future position of the satellites up to 3 to 7 days, and to make this information available to the receiver by occasional download or broadcast, when the mobile is either “hot synced” for a Personal Digital Assistant, or is in the wireless coverage area for a cell-phone. In this paper we have discussed a novel method of coding and conveying the satellite user position in a compact form, with a very simple function of conversion into the standard Kepler parameters. It does not necessitate any exotic or complex satellite position function or predictor, and converts the information into the well known Kepler Ephemeris, thence does not noticeably impact the memory footprint of the mobile, data and code. Moreover, the prediction file residing in the mobile can be “refreshed” using any partial Broadcast Ephemeris Data that would become available during the prediction validity period, and will lead better position accuracy for the rest of the prediction validity period. Simulation results show the effectiveness of the method.
Published in:	Proceedings of the 63rd Annual Meeting of The Institute of Navigation (2007) April 23 - 25, 2007 Royal Sonesta Hotel Cambridge, MA
Pages:	504 - 510
Cite this article:	Garin, Lionel, Venkatraman, SaiPradeep, Gupta, Pramod, "A Novel Ephemeris Extension Compaction/Decompaction Method," Proceedings of the 63rd Annual Meeting of The Institute of Navigation (2007), Cambridge, MA, April 2007, pp. 504-510.
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