Abstract
This study applies the zero-differenced integer ambiguity method, named PPP-Fixed, to extract real-time ionospheric data and eliminate the latencies of rapid/final Global Ionosphere Maps (GIMs). The PPP-Fixed method is also used to derive ionospheric data for post-processed GIM generation, named SGG Post-GIM, combined with low earth orbit satellite data. The obtained hardware delays are applied to revise real-time ionospheric data. Meanwhile, the estimated multi-source ionospheric model is regarded as historical data to estimate an ionospheric prediction model for constraint using the semi-parameter model. Then, the Kalman filter is employed to estimate the parameters to generate real-time GIM. Finally, the accuracy of estimated real-time GIM, named SGG RT-GIM, and SGG Post-GIM is assessed. During the experimental period, the mean differences of SGG Post-GIM and SGG RT-GIM relative to GIMs provided by the international Global Navigation Satellite System service, named IGSG, are −0.46 and −0.57 Total Electron Content Unit (TECU), respectively. The corresponding Root Mean Square (RMS) values are 1.64 and 3.08 TECU. Over the test period, the mean positioning errors of the single-frequency precise point positioning corrected by IGSG, SGG Post-GIM, SGG RT-GIM, and Klobuchar model are 0.14, 0.19, 0.21, and 0.25 m in the horizontal direction, respectively, while the corresponding errors are 0.36, 0.33, 0.38, and 0.64 m in the up direction. Further, the mean biases of experimental days for the self-consistency assessment are 0.06, −0.01, and −0.07 TECU for IGSG, SGG Post-GIM, and SGG RT-GIM, respectively. The corresponding RMS values are 1.19, 1.15, and 1.57 TECU.