Real-Time Precise BDS Clock Estimation with the Undifferenced Observation

We studied and implemented an algorithm for real-time precise satellite clock estimation based on the undifferenced code and phase observations. The BDS and GPS observations of 53 MGEX global sites were collected to generate the real-time clock that was compared with the final WHU 30 s precise clock product. The accuracy of our real-time GPS clock was better than 0.06 ns, comparable to that of the IGS final clock products, which verifies the processing accuracy of our software. The accuracy of the real-time BDS clock was 0.1-0.15 ns, a little worse than that of GPS satellites. A kinematic PPP test showed that, the horizontal accuracy of BDS solution was about 0.041 m, comparable to 0.058 m of GPS solution, while the vertical accuracy is 0.069 m, a slightly worse than 0.037 m of GPS. The kinematic PPP solution based on the real-time clock correction was consistent with the solution based on the final clock products, which verifies the real-time clock products.