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Abstract

The traditional method for retrieving the real-time zenith total delay (ZTD) with GNSS requires stable access to the internet for the reception of satellite orbit and clock corrections. This limits the use of this technique in areas without a reliable internet connection. The new precise point positioning service via the B2b signal (PPP-B2b) service on the Beidou Navigation Satellite System (BDS-3) provides high-accuracy orbit and clock information for GNSS satellites, which offers a promising way to remotely sense atmospheric information with GNSS in real time without the need for internet access. Compared to the post-processed GNSS-ZTDs, the root-mean-square error (RMSE) of the real-time ZTD derived with PPP-B2b corrections is 13.4 mm for the combination solution of BDS-3 and GPS. For 17 stations without the ability to receive PPP-B2b correction in real time, an experiment was conducted with the saved PPP-B2b corrections with our custom-developed receiver and their corresponding observations. For the six stations located in the mid-latitude Northern Hemisphere, the mean RMSE of ZTD was 14.5 mm for the BDS-3/GPS combination solution. However, for stations located in the low-latitude region or Southern Hemisphere, the accuracy of the ZTD was significantly worse than that of the other stations, with a mean RMSE of 23.1 mm. Compared with the ZTD computed from atmospheric reanalysis, the BDS-3/GPS combination PPP-B2b solution has a mean RMSE value of 22.7 mm, which is smaller than that of the GPS-only or BDS-only solution but larger than that of the post-processed ZTD with geodetic benchmark final products.