The Impact of Precise Clock Systematical Bias on Real-Time Precise Point Positioning

In order to meet real-time computation, precise clock is always calculated via single difference observations between epochs, which can avoid the ambiguity parameters and fasten the speed. However, the results of this algorithm are the variation of clock value, hence initial satellite clocks have to be lead-in. Due to the limited precision of introduced value and the nature of time, deviation inevitably exists, no matter what kind of algorithm is used, which results in a systematical bias in precise clock. In Precise Point Positioning (PPP), this systematical bias can be absorbed by ambiguity parameters in phase equations. However, the bias in pseudorange equations can´t be eliminated. As the ambiguity parameters were obtained by pseudorange observations, the systematical bias will have an impact on the ambiguity validation. Three data analysis strategies were carried out to compare the impact of this systematical bias on ambiguity convergence and positions obtained. Strategy 1: PPP with IGS final clock; Strategy2: PPP with systematical bias of 3ns; Strategy3: PPP with systematical bias of 5ns. The impact of this systematical bias to PPP is analyzed by the comparison: with higher systematical bias, convergence time will be longer, to the effect that 3ns systematical bias prolong the convergence time by more than 15%, while the clock systematical bias do not affect the final positioning accuracy.