Abstract
On 31 July 2020, the Beidou global navigation satellite system (BDS-3) was officially announced as being commissioned. In addition to offering global positioning, navigation, and timing (PNT) services, BDS-3 also provides precise point positioning (PPP) augmentation services. The satellite orbit correction, clock correction and code bias correction of BDS-3 and other global navigation satellite systems (GNSS) are broadcast by the BDS-3 geostationary earth orbit (GEO) satellites through the PPP-B2b signal. The PPP-B2b service is available for users in China and the surrounding area. In this study, an initial assessment of the PPP-B2b service is presented, with collected 3-day PPP-B2b messages. Based on broadcast ephemeris and PPP-B2b messages, the precise satellite orbits and clock offsets can be recovered. This precision is evaluated with the precise ephemeris from the GeoForschungsZentrum Potsdam (GFZ) analysis center as references. The results indicate that the accuracy of BDS-3 satellite orbits in the direction of radial, along-track, and cross-track is 0.138, 0.131, and 0.145 m, respectively, and for GPS a corresponding accuracy of 0.104, 0.160, and 0.134 m, respectively, could be obtained. The precision of clock offsets can reach a level of several centimeters for both GPS and BDS-3. Both the performance of static PPP and kinematic PPP are evaluated using the observations from four international GNSS monitoring assessment service (iGMAS) stations. Regarding static PPP, the average convergence time is 17.7 minutes to achieve a horizontal positioning accuracy of better than 0.3 m, and a vertical positioning accuracy of better than 0.6 m. The average positioning accuracy in the direction of east, north, and up-directions are 2.4, 1.6, and 2.3 cm. As to kinematic PPP, the average RMS values of positioning errors in the direction of east, north, and up are 8.1 cm, 3.6 cm, and 8.0 cm after full convergence.
Highlights
The Beidou navigation satellite system (BDS) was independently developed by China to provide positioning, navigation, and timing (PNT) services [1,2]
To evaluate the precision of orbit and clock corrections and precise point positioning (PPP) performance, PPP-B2b messages over a 3-day period were collected from 5 October 2020 to 7 October 2020
There were just 3 epochs of PPP-B2b messages missing, and only PPP-B2b corrections of GPS and BDS-3 satellites were broadcast during the selected period
Summary
The Beidou navigation satellite system (BDS) was independently developed by China to provide positioning, navigation, and timing (PNT) services [1,2]. A three-phase strategy has been adopted in the build-up of BDS, including the Beidou demonstration navigation satellite system (BDS-1), Beidou regional navigation satellite system (BDS-2), and Beidou global navigation satellite system (BDS-3). By the end of June 2020, the whole constellation of BDS-3 was completed, consisting of 24 medium earth orbit (MEO) satellites, 3 geostationary earth orbit (GEO) satellites, and 3 inclined geosynchronous orbit (IGSO) satellites. On 31 July 2020, the BDS-3 system was officially announced as being commissioned. BDS-3 can offer PNT, short message communication (SMC), and international search and rescue (SAR) services. BDS-3 provides a precise point positioning (PPP) service [6,7]
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