Geoid Modelling for Surveying Works Using Satellite Geo-Spatial Data

Positioning is considered as one of the most important problems in civil engineering and surveying works. Today, satellite techniques are widely used for positioning. Global navigation satellite systems provide three-dimensional coordinates (latitude, longitude, and height), related to the reference ellipsoid surface. In most engineering projects, orthometric height related to the geoid is required. separation between ellipsoid and geoid need to be known to convert ellipsoidal height into geoidal height which nearly approximates mean sea level. The ellipsoid is a mathematical surface, while the geoid is a physical one. This leads to problem of modelling the geoid. In this paper, multiple regression method was used to model the geoid in a defined area that resembles a big city. Riyadh city, capital of Saudi Arabia has been used as a case study. It has been found that fifth degree polynomials provide a model with accuracy of 1.8 centimeters.