Determination of Local Geoid with Geometric Method: Case Study

Abstract

Precise determination of a local geoid is of particular importance for global positioning system (GPS) height determination. The geometric method has been widely used for a relatively small area, which interpolates geoid heights based on the GPS-derived heights and leveled heights at some points. To improve the accuracy of a local geoid with the geometric method, several factors should be considered. This paper selects Hong Kong as a test area to study various aspects of the geometric method. These aspects include achievable accuracy, the role of geopotential models, the contribution of terrestrial correction, and interpolation methods. It has been found that incorporation of a geopotential model and the digital terrain model of the area of study can improve the accuracy of the local geoid significantly. An accuracy of 2–3 cm is achievable.