Research On Development Of Elevation Anomaly Interpolation System Based On Regional Quasi-geoid Grid Model

It is difficult to demonstrate the elevation anomaly through a definite formula.Usually,grids are set up with equal distance in the survey area,and then the elevation anomaly data of grid intersection points are obtained through appropriate interpolation methods in the light of the known elevation anomaly data in the area,thus a quasi-geoid grid model of the area is formed,which is then used with the adoption of some interpolation methods to obtain the elevation anomaly at any point in the survey area.The main contents of this study include the method of establishing quasi-geoid grid model,the method of interpolation using grid model,the validity determination of interpolation data of the boundaries of tested areas,the programming and implementation of grid interpolation system and other key technologies,which have been tested and verified by an example of quasi-geoid in Hong Kong.The results of this study are as follows:(1)A set of elevation anomaly interpolation system based on regional quasi-geoid grid model is developed by using object-oriented C# programming language based on Microsoft Visual Studio 2008 development platform.(2)According to the measured GNSS/leveling data in Hong Kong,the quasi-geoid in Hong Kong is simulated by the utilization of the intercept polyhedral function model and the removal-recovery method,reaching the inner coincidence accuracy of 1.1cm and the outer coincidence accuracy of 2.3cm.(3)Accuracy differences of elevation anomaly are tested by utilizing the grid model and the developed interpolation system,and the results show that the median errors of bilinear interpolation,inverse distance weighted interpolation and nearest neighbor interpolation are 1.2cm,1.3cm and 2.7cm respectively.This study draws the following conclusions:(1)The height anomaly interpolation system based on regional quasi-geoid grid model developed in this study can be directly applied in regional geoid refinement,and has the characteristics of friendly interface,high efficiency of interpolation andstable application.(2)Bilinear interpolation method at any point should be selected as much as possible for interpolation of elevation anomaly,and nearest neighboring point interpolation method should be adopted while extracting elevation anomaly date at grid intersections.(3)The quasi-geoid in Hong Kong established in this study meets the precision(5cm)requirement of urban geoid refinement in China.