International Science Community Association Research Journal of Recent Sciences 2277-2502 7 11 2018 11 2 Setting up a geoid model in Cotonou 1 8 EN Degbegnon Léopold 1 Engineer in Geodesy, Department of Civil Engineering of the Polytechnic School of Abomey Calavi, Benin Dognon Awo Martial Arnaud 2 Research Master in Geomatics and Environment, Benin Morou Olivier Da 3 National Geographical Institute of Benin, Benin > Research Paper 2018 9 14 2018 11 2 The reference considered for altimetry measurements in Benin would be accurate only if the geoid of all French West Africa was the same as the geoid of Benin. But it is important to know precisely, the geoid of the place to determine the altitude. The Republic of Benin does not yet have a national model of geoid. The definition and modeling of the geoid of Benin are imperative to facilitate the task to the actors of measurement and localization. To better determine the position of the points to be observed, a theoretical grid of 1km was applied throughout the territory of the Commune of Cotonou and led to the choice of a hundred points. Raw observational data was calculated using PrepaComp software (PrepaComp: Software for switching from Leica GSI format to OBS format) developed by IGN-France for the determination of elevation differences. The geometric geoid determined on the leveled points and the gravitational world geoid will result in two different reference planes. The gap between these two planes is called the trend. The undulation N of the geometric geoid at each of these points has been determined. So the geoid Nglc_2017 (Rippling of the local geoid of Cotonou) determined is an accuracy of two centimeters (2cm). Copyright@ International Science Community Association