Abstract
Tropospheric delays are one of the main sources of errors in the Global Navigation Satellite System (GNSS). They are usually corrected by using tropospheric delay models, which makes the accuracy of the models rather critical for accurate positioning. To provide references for suitable models to be chosen for GNSS users in China, we conduct herein a comprehensive study of the performances of the IGGtrop, EGNOS and UNB3m models in China. Firstly, we assess the models using 5 years’ Global Positioning System (GPS) derived Zenith Tropospheric Delay (ZTD) series from 25 stations of the Crustal Movement Observation Network of China (CMONOC). Then we study the effects of the models on satellite positioning by using various Precise Point Positioning (PPP) cases with different tropospheric delay resolutions, the observation data processed in PPP is from 21 base stations of CMONOC for a whole year of 2012. The results show that: (1) the Root Mean Square (RMS) of the IGGtrop model is about 4.4 cm, which improves the accuracy of ZTD estimations by about 24% for EGNOS and 19% for UNB3m; (2) The positioning error in the vertical component of the PPP solution obtained by using the IGGtrop model is about 15.0 cm, which is about 30% and 21% smaller than those of the EGNOS and UNB3m models, respectively. In summary, the IGGtrop model achieves the best performance among the three models in the Chinese region.
Highlights
Tropospheric delays are some of the most significant error sources in the data analysis of the space geodetic observations like satellite navigation
The results show that the differences between the Global Positioning System (GPS)-derived Zenith Tropospheric Delay (ZTD) and IGS final ZTD products from4 mm to 13 mm with the mean value of about 0.5 mm and mean Root Mean Square (RMS) of about 4.9 mm, and vary from −4 mm to 13 mm with the mean value of about 0.5 mm and mean RMS of about 4.9 mm, thisand indicates a comparable accuracy with the IGS final ZTD product
We found that the Precise Point Positioning (PPP) solutions based on IGGtrop seem to converge faster than those of the EGNOS and UNB3m models implying that the IGGtrop model can accelerate the convergence time compared to the EGNOS and UNB3m models at these exemplary stations
Summary
Tropospheric delays are some of the most significant error sources in the data analysis of the space geodetic observations like satellite navigation. Some navigation tasks like real-time Positioning, Navigation and Timing (PNT) applications require users to process the data in real-time mode, so choosing a more accurate empirical model to mitigate the tropospheric delay will be necessary and crucial for real-time PNT users [2,3,4,5]. The commonly used empirical tropospheric delay models include: the UNB models (UNB1 through UNB4) and the EGNOS model [6,7,8,9,10], which is the WAAS version of UNB3m, etc. As latitude-only based models, the UNB3m and EGNOS models often cause large biases in some areas
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