Prediction of SBAS Integrity Performance using PORIMA Algorithm

H. Su

Abstract:	The paper presents an independent method using the PORIMA algorithm to predict SBAS integrity performance regarding protection levels and to provide timely warnings when SBAS integrity performance declines for an assigned flight phase in close future. PORIMA is a user integrity monitoring and prediction algorithm developed by Thales Air Systems[6][8][9]. The algorithm uses differences between the GPS broadcast ephemeris and precise predicted orbits to determine the thresholds of measurement errors due to satellite orbit and satellite clock errors as well as troposhreic, ionospheric and multipath errors and compute the related protection levels for a user location in real-time. The accuracy of a GPS predicted orbit can reach a level of about 24 ± 6 mm, much higher than the accuracy of the broadcast ephemeris, therefore the predicted GPS orbit is able to be used as reference for analysis of the performance of the GPS broadcast ephemeris both in real time and in advance. The exact impact of GPS SIS (Signal-in-Space) errors on a user location can be determined in advance and therefore the GPS integrity performance in terms of protection levels can be predicted earlier than the actual SBAS real-time results. The system fault models are considered. The errors such as tropospheric and multipath etc. are corrected according to SBAS models[3] and the ionospheric effects are calculated using the broadcast Klobuchar model. With civil dual frequency code measurements, the impact of ionospheric errors would even be smaller.
Published in:	Proceedings of the 23rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2010) September 21 - 24, 2010 Oregon Convention Center, Portland, Oregon Portland, OR
Pages:	2056 - 2063
Cite this article:	Su, H., "Prediction of SBAS Integrity Performance using PORIMA Algorithm," Proceedings of the 23rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2010), Portland, OR, September 2010, pp. 2056-2063.
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