Refined troposphere delay models by NWM ray-tracing for pseudolite positioning system and their performance assessment

Abstract

Pseudolite positioning system can enhance GNSS (Global Navigation Satellite System) by improving satellite geometry and providing services independently in the GNSS unavailable environment. Many error items of pseudolite positioning system, e.g., tropospheric delay error, need to be corrected by an accurate model. While several tropospheric delay models suitable for pseudolite positioning systems have been proposed, the key parameters indicating the upper boundaries for tropospheric refraction are fixed to an experimental value in these models. In this paper, we studied the spatiotemporal characteristics of the upper boundary heights for hydrostatic and wet tropospheric delay based on the ERA5 global meteorological reanalysis data. With the refined height boundary term, we refine four existing tropospheric delay models for pseudolite positioning systems, including RTCA, MRTCA, Bouska and Hopfield models. To evaluate the performance of the refined models, we selected 12 airports distributed globally as experimental areas and analyzed the error characteristics of the four refined tropospheric models and the LTC model (independent of height). The experimental results show that when the slant distance between the pseudolite base station and the receiver is constant at 5 km, the MRTCA model has the best performance, with an RMSE (root mean square error) of about 0.15 m. When the elevation angle between the pseudolite base station and the receiver is constant, the RMSE of the LTC model is the smallest at the low elevation angle, and the RMSE of the MRTCA model is the smallest at the high elevation. The RMSE of pseudolite tropospheric delay models show seasonal variation.