Local geoid determination using RBF method and GPS/gravity data: a case study in ShenZhen(China)
20/09/2016 | 16:30 | Session 3: Local/regional geoid determination methods and models
Author(s): Chanfang Shu and Zhuoran Ji
Chanfang Shu and Zhuoran Ji
Geoid determination is one of the main tasks of establishing a modern geodetic datum. Some standard methods, such as the numerical integration method and least-squares collocation (LSC), are widely used to determinate local/regional geoid together with the remove-compute-restore (RCR) technique. In recent years, the parameter estimation method using radial basis functions (RBF) has been extensively used in local/regional gravity field modeling. In this paper, RBF method is used to determinate local geoid with GPS/gravity data, and two critical issues of RBF method (the number and spatial distribution of RBFs, the bandwidth parameter estimation) are studied and discussed detailed. For the heterogeneous data distributions in this case, Reuter grid is used to design RBF network. The performance of the two different basis functions (IMQ and Poisson kernel) and the different number of RBF’s center are compared and discussed. By establishing a linear relationship between the spatial distribution of the RBF’s centers and the bandwidth parameter, the bandwidth parameter estimation is converted to the determination of the scale factor k. Three methods (Generalized cross validation, Minimum condition number of design matrix, Control Point) are comparatively used to determining the scale factor k. The research result shows that the influence of the scale factor k on the precision of geoid determination is greater than the number of RBF’s center. On the whole, the determination of the scale factor k by using GPS/leveling control points and minimum condition number of design matrix are both better than generalized cross validation (GCV). In this case, 4870 GPS/Gravity data (Spatial resolution is about 1km) are collected and used to determinate local geoid, and 65 high precision GPS/leveling data are used for evaluation accuracy. The precision of geoid determination in ShenZhen is about ±3cm by using RBF method.