A Study into the Use of URA in Satellite Selection

John W. Lavrakas and Chris Shank

Abstract:	The GPS Control Segment’s User Range Accuracy (WA) algorithm was improved two years ago in order to better reflect the error estimate for which the Space and Control Segments are responsible. This paper reviews the changes to this algorithm, identifies each component in the URA error budget, and explains some satellite and MCS anomalies affecting this statistic. The User Segment, both those using precise positioning service (PPS) and those using standard positioning service (SPS), may use this information in their satellite selection process, as protection against Control and Space Segment-induced range. errors and to optimize their navigation solution. Using data collected from the MCS Kalman filter from the five worldwide monitor stations, this paper analyzes the use of URA in satellite selection over optimum positional dilution of precision (PDW , recommending that a hybrid URAIPDOP algorithm be implemented in the satellite selection process.
Published in:	Proceedings of the 49th Annual Meeting of The Institute of Navigation (1993) June 21 - 23, 1993 Royal Sonesta Hotel Cambridge, MA
Pages:	261 - 270
Cite this article:	Lavrakas, John W., Shank, Chris, "A Study into the Use of URA in Satellite Selection," Proceedings of the 49th Annual Meeting of The Institute of Navigation (1993), Cambridge, MA, June 1993, pp. 261-270.
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