Residuals overbounding modeling of the tropospheric delay models

doi:10.11947/j.AGCS.2023.20220231

Abstract

Abstract: The satellite signals of the global navigation satellite system (GNSS) will be delayed when traveling through the troposphere, and these delays can be corrected by using empirical models. To ensure safe and reliable positioning, an overbounding model of tropospheric delay residuals after model correction should be established to monitor the integrity of positioning services. The radio technical committee for aeronautics (RTCA) recommended that the overbounding standard deviation of the zenith tropospheric delay used in aviation is 0.12 m. However, this constant value does not consider the geographical and seasonal variation of the tropospheric delay residuals, which would reduce the continuity and availability of GNSS in safety of life (SoL) applications. Considering the geographical and seasonal variations of the tropospheric delay residuals, the extreme value analysis is used to establish the overbounding model of the tropospheric delay residuals. Firstly, total 18-year residuals were standardized for each 10° latitude band to extract the seasonal variation. Then the general extreme value (GEV) distribution was fitted to the annual maximum and minimum values of the standardized residuals, and the extreme values at a probability of 10^-7 were calculated with the fitted parameters. Finally, the extreme values were converted to the overbounding standard deviation. The overbounding models of three tropospheric delay models, including GPT2w, UNB3 and Saastamoinen, are established by using this method, and the bounding performance of these models is validated by using the international GNSS service (IGS) tropospheric delay products. The residuals show that the overbounding model is conservative and available. For the UNB3 model, the calculated range of overbounding standard deviation is 0.05~0.12 m, which decreases by 4.1% to 57% compared with the constant value of 0.12 m specified by MOPS, effectively improving the continuity and availability of GNSS service in SoL application. For GPT2w and Saastamoinen models, the range of overbounding standard deviation is 0.03~0.08 m and 0.06~0.14 m, respectively.

Key words: integrity, residual tropospheric delay, overbounding model, GEV

CLC Number:

P227

FU Yunri, YANG Ling, SHEN Yunzhong, LI Bofeng. Residuals overbounding modeling of the tropospheric delay models[J]. Acta Geodaetica et Cartographica Sinica, 2023, 52(6): 895-903.

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