Research On Inversion Method Of Underwater Gravity Field Based On GNSS Reflected Signal

The realization of gravity anomaly inversion based on Global Navigation Satellite System(GNSS)reflected signal data is a new direction of its application research in the field of marine remote sensing.In this paper,based on GNSS reflection signal measurement data,we carried out research on methods such as geoid height error model construction,water surface reflection point calculation,multi-source water surface altimetry and gravity anomaly inversion.The main contents and results are as follows:(1)The inverse Venning-Meinesz method,Sandwell method based on vertical deviation inversion of gravity anomaly,and the inverse Stokes method based on geoid height inversion of gravity anomaly are analyzed.In order to achieve the purpose of inversion of gravity anomalies with high surface water data,the gravity anomaly inversion method and influencing factors based on the removal-recovery inverse Stokes theory are mainly studied.The simulation results show that under the same integration area condition,the higher the removal order of the model,the higher the recoverable ratio;under the same model removal order condition,the larger the integration area,the model recoverable ratio The higher.(2)According to the characteristics of satellite water surface reflection signals,the feasibility plan of water surface height measurement was studied,the advantages and disadvantages of each height measurement program were analyzed and compared,the experimental height measurement program in this paper was proposed,and various errors in the process of water surface height measurement were constructed.Correction model of height measurement error.Combined with the knowledge of traditional physical geodesy and considering the influence of sea surface topography,the error model of water surface height and geoid height was constructed.The research results show that under shore-based experimental conditions,the altimetry deviation caused by atmospheric pressure and effective wave height can be up to about 4.7m;the influence of sea surface topography on the geoid can reach up to about 2m.(3)In order to obtain high-precision,high-stability reflection points on the water surface,the experimental comparison method was used to analyze the modified iterative S.C.Wu algorithm,the bisection iterative line segment bisection algorithm and the angle bisection algorithm.Considering the land-based experimental environment,a single-star water surface altimetry error model was constructed.Based on the single-satellite altimetry model and the experimental environment,the multi-source water surface altimetry technology was studied.For the difference in the altimetry of each satellite,a satellite weight solution algorithm based on time delay equivalent is proposed,and the multi-source water altimetry was further constructed The model achieves the purpose of simultaneously processing multi-source satellite signals and high-precision multi-source water surface height measurement.The experimental results show that,compared with the line segment dichotomy algorithm,the stability of the reflection point calculation based on the angle dichotomy method is better;in a multi-source water surface altimetry environment,compared with the arithmetic average method,the timedelay weighted average method is used for the accuracy of water surface measurement higher.(4)In order to further verify the algorithms proposed in this paper,including water surface reflection point solution,multi-source altimetry,gravity anomaly inversion,etc.,the groundlevel experiments were carried out in an open water using the first 720 calculation results of the EGM2008 model as the true values.The experimental results show that the average stability of the water surface reflection point calculated based on the angle dichotomy method is better;compared with the single system water surface height measurement,the multi-source measurement accuracy can be improved by about 15.6%;compared with the arithmetic average height measurement method,the time The precision can be improved by the extended weighted average method by about 7.31%;under certain conditions in the integration area,the gravity anomaly inversion accuracy is related to the model removal order.The higher the removal order,the higher the inversion accuracy.When the model is removed The first 500 steps of the removal-recovery calculation,the difference between the calculation result and the true value is about 2.37 m Gal.