Research and Implementation of BDS/GPS Coarse Time Navigation Algorithm

When the receiver cannot demodulate satellite signal transmission time, positioning can be completed with a combination of code phase measurement and auxiliary information, that is, coarse time navigation (CTN). Assistant information includes ephemeris, priori position, and coarse signal transmission time. For the GPS systems, requirement of the position and time precision is 100 km and 1 min. This paper attempts to determine the allowed priori position and coarse time error range of BDS and has realized the GPS/BDS coarse time navigation algorithm and carried out experimental verification using the measured data of IGS CUT0 station. The results show that BDS, GPS, and BDS/GPS coarse time navigation positioning precision is equivalent to their pseudorange positioning precision. Dual system CTN can effectively improve positioning precision, which is better than the precision of single system pseudorange positioning or coarse time navigation. Conclusion is that BDS/GPS coarse time navigation is an effective method without pseudorange and that dual system navigation is easier to receive enough visible satellites.