USING SURFACE FITTING AND BUFFER ANALYSIS TO ESTIMATE REGIONAL GEOIDAL UNDULATION

Fang-Shii Ning

doi:10.1590/s1982-21702015000300035

Abstract

Abstract:Geoidal undulation is the distance from the surface of an ellipsoid to the surface of a geoid measured along a line that is perpendicular to the ellipsoid. This paper describes how the geoidal undulation can be derived from the orthometric height, Global Navigation Satellite System geodetic height, and a surface model. Various surfaces fitting using the plane coordinates of the reference points and analysis with different buffers were used to determine the geoid undulation Taiwan. The results show that the quadratic surface model outperformed other surface models, yielding a buffer radius ranging from 15 to 25 km. According to the results, the accuracy of regional geoid undulation (city or state) can be improved through this process of surface fitting

Highlights

Taiwan is an island in East Asia with a total area of approximately 3.6 million hectares.Approximately 70% of Taiwan is covered with mountainous terrain
This paper describes how the geoidal undulation of a point can be derived from the orthometric height, the GNSS geodetic height, and a surface model
For the sake of parsimony, the quadratic surface method is optimal for determining regional geoidal undulation

Summary

Introduction

Taiwan is an island in East Asia with a total area of approximately 3.6 million hectares. 70% of Taiwan is covered with mountainous terrain. In Eastern Taiwan, the average height of the mountains near the coast is approximately 2000 m (Chen et al, 2011). The western area of Taiwan is predominantly a flat region (Figure 1). Obtaining the orthometric heights of benchmarks and monuments by using spirit levelling costs time and manpower. The geoidal undulation can be computed using several techniques, for example, by using the numerical integration of Stokes’ formula directly, fast Fourier transform, least squares collocation, spherical harmonic functions developed in a series, or by direct calculation of the difference between the ellipsoidal heights (from Global Navigation Satellite System – GNSS) and orthometric height (from spirit leveling)(Hwang et al, 2013)

Methods

Results

Conclusion