Validation and Calibration of Tropospheric Wet Delay Models over Nigeria Using GPS Data

Tropospheric delay play a critical role in satellite communication. Due to lack of measuring instruments, tropospheric wet delays are often estimated using empirical models. In this study, we investigated the performance of four (Saastamoinen, Callahan, Mendes, and Berman) models in four tropical locations within Nigeria. By comparing with GPS data, our results showed that the models generate errors on the same magnitude as the measurement data. The Saastamoinen and Mendes models were found to have the best performance amongst the four models at the monthly and annual scale. At the annual scale, RMSE values of 0.12–0.18 and 0.11–0.16 were obtained for Saastamoinen and Mendes models, respectively, compared to 0.19–0.29 for both Callahan and Berman models. In order to improve the performance of the wet delay models, calibration of their parameters was carried out. It was observed that the new parameters improved the performance of the models significantly. The results in this study will help reduce the uncertainties associated with estimating wet delays in tropical regions.