Analysis on the improvement of BDS-3 satellite to BDS global positioning service

With the continuous development and networking of the BeiDou Navigation Satellite System(BDS), BDS-3 satellites has begun to participate in the provision of global positioning service. In the case, the positioning performance of BDS has become the main focus of the both GNSS researchers and users. In order to evaluate the global positioning accuracy and availability of BDS, 44 IGS stations which can receive signals from both BDS-2 and BDS-3 satellites are selected in this study for the experiments, standard single point positioning based on B1I, B3I and B1I／B3I ionosphere-free observables are carried out respectively. Meanwhile, the broadcast ephemeris is also used to perform the global distribution of visible satellites and PDOP values of BDS. The results show that BDS-3 increases 2 ～ 4 visible satellites to BDS-2 only solutions with reducing PDOP values and positioning noises. As a result, BDS-3 expands the service range of BDS system from the Asia-Pacific region to all of the world. In addition, in the global scope, horizontal accuracy of 1.5m and vertical accuracy of 3 m can be achieved by using dual frequency ionosphere-free combination while 2.5 m and 4m can also be achieved in the case of single-frequency counterparts. We also implement a hand-held dynamic experiment and the results show that a positioning accuracy of 2 m and 4m for the horizontal and vertical components can be achieved under the dynamic conditions. In general, BDS can provide global positioning service with the accuracy of 2 m and 4 m for the horizontal and vertical directions using pseudorange standard single point positioning, which can meet the positioning needs of most users.