Study on Identification Parameters and Updating Mechanism of Beidou Navigation Message

In the application of high-precision satellite navigation and positioning, differential GNSS positioning technology is used to eliminate the influence of various errors in order to improve the performance of positioning accuracy. The mathematical physics of differential GNSS positioning technology is based on the same space-time datum (the same orbit and difference parameters). Thus, in the RTCM/RTCA differential protocol, an IOD field is constructed based on the parameters of the GNSS navigation message parameters. The base station transmits the IOD parameter to the rover and compare it with the IOD parameters that formed by rover itself, then it can determine whether they are using the same ephemeris and clock difference parameters. The IOD field in the differential protocol is generally constructed based on a unique parameter in the GNSS navigation message for a certain period of time. There is no special field used to identify the parameter group in the BeiDou navigation message. Therefore, it is necessary to analyze the parameters of the existing navigation message, discuss the mechanism of parameter formation and constrain the broadcasting mechanism of the message so as to solve the obstacles in the scale application of BeiDou high precision differential. In this paper, the technical background of BeiDou RTCM IOD is discussed, the solution is studied and the experimental results show that it is feasible and effective to construct BDS RTCM IOD parameters based on Toe.