GPS range error analysis based on navigation message representation

Aiming at the new CNAV/CNAV-2 navigation message format in the GPS modernization process, the current GPS navigation message format and the new format in data expression were compared. To evaluate the navigation and positioning influence of different data truncated ways, the concept of truncation error was brought up to analysis the problem. The actual RINEX navigation data was utilized for generation, processing two message structures; range errors caused by ephemeris and clock parameters truncation were compared between NAV and CNAV/CNAV-2 message. Results show that CNAV/CNAV-2 range error caused by parameters truncation is smaller than NAV message. NAV message is more sensitive to truncation errors. Meanwhile, to CNAV/CNAV-2 message ephemeris parameters truncation can improve range error up to a centimeter level, clock parameters truncation can improve range error up to a decimeter level. Thus, clock representation accuracy should be improved with priority in limited bandwidth circumstance. More significant improvements of the accuracy can be achieved by adjusting the representation of the satellite clock parameters.