Troposzferikus maradék ellentmondások becslése az életbiztonságra veszélyes GNSS-alkalmazások esetén

Abstract

In safety-of-life navigation applications of GNSS the major concern of the user is not the accuracy, but rather the integrity of the positioning service. To assess integrity, the protection level that bounds the positioning error even at very small probability levels must be determined. Recent studies show that – due to the emerging multi-frequency civilian signals – the tropospheric delay will become the most significant error source, especially at low elevation angles. The RTCA MOPS (Minimum Operational Performance Standard) for GNSS systems in aeronautics specifies a global constant for the maximum tropospheric residual error in the zenith direction. Recent studies suggest that this value is too conservative in many regions of the globe leading to lower availability and continuity of the positioning service. To overcome this limitation, a new residual tropospheric error model has to be formulated, that considers both the geographical and the seasonal variations of the tropospheric delay model performances. Our study focuses on the development of an advanced residual tropospheric delay error model (ARTE) using the methodology of extreme value analysis for the RTCA MOPS troposphere model. The developed ARTE model was validated with IGS zenith total delay (ZTD) estimates and numerical weather models obtained in a case study of extreme weather in Central-Europe. The results show that the proposed model maintained the conservatism of the original model, nevertheless yields a significantly lower residual error estimate in many regions of the globe.