Reference Ellipsoid Parameters of Cameroon from GPS Data

Abstract

The standard spheroidal reference surface also referred as the reference ellipsoid is a part of mapping basic infrastructures of a country. In Cameroon, the ellipsoid Clarke 1880 with unknown parameters used for a long time as reference system in basic mapping, has lead to the use of World Geodetic System 1984 (WGS 84) whose parameters are well known. Meanwhile, the latter is not accurate locally due to the fact that the best ellipsoid is the one that fits very well with the local geoid. In order to look for the parameters of the local ellipsoid that fits best to the local geoid (Cameroon Geoid Model 2011 (CGM11)), the Global Positionning System (GPS) data made of 525 geodetic ground control points of the new geodetic network of Cameroon set up in 2011 were used. These GPS measures provide for each point the values of the ellipsoid height and the elevation which are used to determine the parameters of the local ellipsoid model for Cameroon through the least square form of the Molodensky analytical method. The results are given as the difference in ellipsoidal height relative to the parameters of the WGS84 ellipsoid assuming the two ellipsoids in their parallel. These results show that the obtained ellipsoid fits better to the local geoid with 1.072 m as the standard deviation value, is improved considerably in comparison to the previous studies conducted in Cameroon whose standard deviation was fairly equal to 1.679 m.