| Low Earth Orbit(LEO)satellites are expected to solve the problem of too long convergence time for GNSS Precise Point Positioning(PPP)technology due to its relatively low orbit height,fast movement speed,and reduced signal power attenuation.Improve the positioning accuracy of special areas.However,the existing GNSS/LEO PPP simulation mainly considers the impact of the ideal LEO constellation on PPP after the addition of the ideal LEO constellation.Due to the lack of real LEO constellation orbit data,it is difficult to accurately evaluate the PPP performance of the LEO constellation.Therefore,it is necessary to carry out research on the GNSS/LEO PPP simulation technology considering the LEO satellite orbit error to provide support for the deployment of China’s low-orbit satellite Internet constellation and high-precision positioning applications.The main work and innovations of this paper are as follows:(1)Established PPP observation model and GNSS/LEO PPP model,built GNSS/LEO PPP simulation platform,analyzed the performance of GNSS/LEO combined PPP and LEO constellation independent PPP,and evaluated the effect of different Walker Star LEO constellation configurations on GNSS /LEO PPP performance impact.The results show that under the GNSS/LEO constellation configuration,the PPP convergence time in low latitudes is significantly correlated with the Walker Star LEO constellation configuration.When the number of LEO constellation orbital planes is greater than 4 and the number of satellites reaches 192,the PPP convergence time in low latitude areas is less than 180 s,and gradually stabilizes;for the total number of satellites of 242 independent LEO constellations,the PPP convergence time of the high,middle and low latitude stations are respectively It can reach about 80 s,172.5s and 250.5s.(2)Aiming at the fact that the current GNSS/LEO post-PPP simulation conditions are too ideal and the LEO satellite orbit error is not considered,a PPP analysis method based on the measured LEO satellite orbit error is proposed.According to the characteristics of the orbit determination error,a LEO satellite orbit determination error correction model based on the EMD+harmonic model is constructed.The simulation results show that the measured LEO satellite orbit determination error will significantly increase the GNSS/LEO PPP positioning error and increase the PPP convergence time;after adopting the LEO satellite orbit determination error correction model based on the EMD+harmonic model,the GNSS/LEO combined PPP and LEO constellation The independent PPP positioning error correction effect reached 13.36% and 10.35%,and the improvement effect of the convergence time reached 15.51% and 26.16%,respectively.(3)Starting from the need to consider the LEO satellite orbit prediction error during real-time PPP simulation demonstration,a PPP analysis method based on the measured LEO satellite orbit prediction error is proposed.The effect of LEO satellite orbit prediction error on independent PPP performance of LEO constellation is simulated and analyzed,and the relationship curve between prediction time and PPP positioning error is calculated.The results show that the PPP positioning error gradually increases with the increase of the forecast duration and the quadratic coefficient of the orbit prediction error range;due to the characteristics of the Walker Star constellation,when the forecast duration and the orbit prediction error range quadratic coefficient are the same,high latitude areas The PPP positioning error is the smallest,followed by mid-latitudes,and the PPP positioning error is the largest in low-latitude areas. |
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