Performance evaluation of GNSS ionospheric constraint single-frequency PPP

In allusion to two commonly used models in single frequency precise point positioning (SF-PPP): SF-PPP with raw and uncombined observations(SF-UC-PPP) and SF-UC-PPP with the constraint of ionospheric delay, considering simultaneously the three different ionospheric delay constraint strategies including constant, step wise relaxed and spatial-temporal strategy, these models are compared and analyzed in positioning accuracy and convergence time using GPS and GPS+BDS data. The experiment result shows that by using the GPS system observations these three models with ionospheric delay constraint can significantly improve the convergence speed of PPP, the step wise relaxed model is the fastest. Its average convergence time is 32.36 min. Accuracy of these four models after convergence is roughly equivalent. By adding the BDS data, the convergence time of these models increases differently. The spatial-temporal model has the most significant improvement, which convergence time is shorted to 59.22% of single system. Aafter the using of BDS data, the accuracy of horizontal direction is improved by 0.5 cm to 1.3 cm, the vertical accuracy has slight decrease.