Performance analysis of two RDSS positioning modes of BeiDou-3 system

The BeiDou-3 global satellite navigation system (BDS-3) provides two radio determination satellite service (RDSS) positioning services for users, i.e., the traditional RDSS (TRDSS) positioning of the BeiDou-2 regional satellite navigation system, and the comprehensive RDSS (CRDSS) positioning, which integrates the RDSS and radio navigation satellite service. As published studies regarding the RDSS positioning service are few, we analyze and compare the performances of the two RDSS positioning modes. First, we systematically investigate the principles of the TRDSS and CRDSS positioning, and then analyze the evaluation methods in terms of their positioning accuracy, real time, and coverage range. Second, based on the BeiDou RDSS measured data, we evaluate the performances of the TRDSS and CRDSS positioning. Compared with TRDSS positioning, CRDSS positioning exhibits the following: 1) A significant increase in positioning accuracy, resulting in error improvement from 8 to 2~m and root mean square improvement from 3.13 to 0.85~m; in other words, the positioning error, constant deviation, and stability improve significantly. 2) The real time reduces slightly from 1.1 to 1.8~ns, which is within the acceptable range. 3) The coverage range expands from the areas of 62 ${}^{\circ }$E–145 ${}^{\circ }$E and 5 ${}^{\circ }$N–55 ${}^{\circ }$N to the areas of 50 ${}^{\circ }$E–170 ${}^{\circ }$E and 0 ${}^{\circ }$N–70 ${}^{\circ }$N, respectively. 4) CRDSS positioning is not restricted by the constraints of the digital elevation database or the user elevation information and can thus solve the occlusion problem effectively.