The Best Surface Fitting of Regional Geoidal Undulation- A Case Study of Taichung Area

The geoidal undulation of points can be derived from orthometric height and GNSS geodetic height. The geometric method can produce geoidal undulation more accurate and faster than gravimetric method in the area with GNSS data and levelling data. In this research, we use different surface models to find out the best fitting surface based on geometric method to interpolate geoidal undulation of unknown point. The result shows quadratic surface method is the best one to solve regional geoidal undulation in terms of both costs and benefits.