Better thresholds and weights to improve GNSS PPP under ionospheric scintillation activity at low latitudes

Ionospheric scintillation can degrade the global navigation satellite system ( GNSS) measurement quality and even result in loss of signal lock, thus degrading the accuracy and reliability of GNSS precise point positioning (PPP). To reduce the adverse effects of scintillation on GNSS PPP, we propose an improved strategy consisting of two steps: (a) determining the appropriate threshold values in cycle slip detection to avoid frequent misjudgment of cycle slip detection and (b) applying the suitable stochastic model to assign the appropriate weights for the affected measurements caused by scintillation. The performance of our proposed strategy is validated by using 1 month of global positioning system (GPS) data collected by the ionospheric scintillation monitoring receiver (ISMR) installed at Hong Kong from October 19 to November 19, 2015. The analysis indicates that the improved strategy can effectively mitigate the adverse effects of ionospheric scintillation on PPP solution. The root-mean-square (RMS) statistics show that the accuracies of our improved PPP solution in the horizontal and vertical components are better than 0.05 m and 0.1 m in general even under strong scintillation conditions. Compared with the conventional PPP solution, the proposed strategy can improve the positioning accuracy by approximately 52.6%, 48.8%, and 50.0% in the horizontal, vertical, and 3D components, respectively.