A New User Integrity Prediction and Monitoring Algorithms for Aviation Application

H. Su, W. Ehret

Abstract:	The paper presents new user integrity prediction and monitor algorithms for aviation applications - PORIMA ( Precise Predicted Satellite Orbit based Receiver Integrity Monitoring Algorithm). Using the PORIMA for GNSS SIS integrity monitoring and satellite failure detection, the thresholds of user satellite measurement errors can be determined based on the differences between the broadcast ephemeris and the precise predicted orbits and mapped to user locations. The actual user satellite measurement errors at each epoch are obtained from the measurement residuals of the user navigation solution or PVT (Position, Velocity and Time Solution). If the satellite measurement errors are larger than the thresholds, the related satellites are labeled as “bad” satellites and those measurements will be removed from the navigation solutions or PVT. After removing “bad” measurements, the navigation solution at that epoch will be performed again and the related protection levels are calculated as well. In such a way, the satellite failures such as satellite maintenance anomaly, satellite manoeuvre, satellite clock jump and signal distortion etc. can be easily detected. The paper also presents an approach to use PORIMA for GNSS SIS integrity prediction. As IGS GPS ultra-rapid orbits are predicted for at least 24 hours in advance and the broadcast ephemeris transmitted by GPS satellites are updated at least in two-hourly intervals. Therefore using PORIMA, the actual broadcast ephemeris and the precise predicted orbits, the user integrity performance in the next six or more hours in terms of protection levels can be predicted. Since precise predicted GNSS orbits are used as reference, the user receivers are able to determine the exact impact from GNSS SIS errors on the user navigation performance. Therefore using PORIMA, the users can achieve better performance of the integrity monitor and satellite failure detection than using RAIM. In fact the performance is near SBAS levels. Other errors such as ionospheric, tropospheric and multipath effects etc. can be corrected using SBAS model (ref. RTCA MOPS D229). With civil code measurements from L2 or L5, the performance of PORIMA can even be further improved.
Published in:	Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009) September 22 - 25, 2009 Savannah International Convention Center Savannah, GA
Pages:	1396 - 1403
Cite this article:	Su, H., Ehret, W., "A New User Integrity Prediction and Monitoring Algorithms for Aviation Application," Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009), Savannah, GA, September 2009, pp. 1396-1403.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In