Study On The Refinement Of Quasi-geoid With Satellite Gravity Data Combination

The regional geoid determination involves different kinds of data and complex computations. At present, the most commonly used method to establish regional geoid model is based on geometric and gravity method, combined with the gravity data, DTM/DEM data and the earth's gravity field model combination to achieve regional geoid refinement. But the ground measured gravity data exist the problems of uneven data distribution and is difficult to get, with the development of satellite gravity data in the two aspects of accuracy and resolution of the rapid increase, and gravity data is increasingly rich and integration. The goal of this paper is how to realize the gravity of information with different frequency, height, error characteristics of effective integration, to eliminate the differences between the data in the fusion process, so as to obtain reliable and uniform basic gravity data, the results should be used for constructing the regional geoid. The main contents of this paper are as follows:(1) A detailed analysis of the gravity field of the spherical harmonic function, fully normalized associated Legendre function is derived.we use EGM2008 as a reference gravity field and introduce iteration method to complete satellite gravity data self-adaption fusion.We make these methods supplement themselves.Compare and analysis two selection regions in Beibu Wan. From the conclusion, large deviation between old and new model is with in less than 180 orders, and fusion of local gravity field has been significantly refined.(2) In the realization of Multi-source gravity data combination, study on the relationship between the precision of gravity data, DEM terrain data and regional gravity geoid determination. Through the calculation of terrain indirect impact value, terrain directly impact value, terrain correction value and the residual geoid undulation, analysis of factors that determine the various components and the effect of gravity geoid. In the derivation of the specific terrain conditions, all kinds of data and analysis of the relationship between accuracy and model matching, Construction of data from specific technical index estimation strict simulation algorithm model is the accuracy of the results. It means that, in the future geoid modeling, this method can be used to combine with the terriestral gravity or to be a substitute one in the area with no terriestral data.(3) Design and development geoid software, verification the software by a project experimental, analysis minutiae features of causal relationship between observational data and model accuracy, and achievement by specific technical in dicators of the observational data to accuracy of model results to estimate model accurate and simulation optimal design. Results can verification that by using EGM2008 model to determine geoid is the highest precision fitting method. The results also demonstrate the use of geoid refinement software, combined with an adaptive fusion local gravity data and DEM terrain data, can basically meet the centimeter level geoid refinement requirements.