A new simplified zenith tropospheric delay model for real-time GNSS applications

We have proposed a new simplified zenith tropospheric delay model for Global Navigation Satellite System (GNSS) real-time applications using 10 years of numerical weather prediction data from the National Center for Environmental Prediction (NCEP). Our proposed model is a blind model in which the atmospheric input parameters are tabulated based on realistic atmospheric behavior. The model with only 108 meteorological parameters is as simple as UNB3m model but has better performance; thus, it has great potential to be widely hardwired in GNSS receivers. Additionally, the accuracy of the new model is better than that of the state-of-the-art model named GPT2w in terms of the zenith tropospheric hydrostatic delay (ZHD) prediction, particularly at high altitudes. The proposed model is validated using NCEP reanalysis data and GNSS-derived International GNSS Service data. In comparison with the NCEP reanalysis data, the new model demonstrates an approximately 23% improvement in the root mean square (RMS) and a 76% improvement in the bias compared with the UNB3m model at the surface level. More significantly, this model performs better than the GPT2w model with respect to the ZHD prediction with increasing altitude, achieving up to a 96% improvement at an altitude of 10 km. The results of the zenith tropospheric delay (ZTD) model are compared with those derived from GNSS data. Notably, the RMS error and bias of the proposed model (with average values of 4.2 cm and 0.3 cm) are lower than those of the UNB3m model (with values of 5.0 cm and 1.0 cm), respectively.