Comparative Analysis of Three Plane Geometric Geoid Surfaces for Orthometric Height Modelling in Kampala, Uganda

Abstract

The conversion of theoretical, as well as geometric heights to practical heights requires the application of geoidal undulations from a geoid model. The various global geopotential models that are readily available for application in any part of the world do not best-fit regions, as well as countries. As a result, there is a need to determine the local geoid models of local areas, regions and countries. This study determines the local geoid model of Kampala in Uganda for orthometric heights computation by comparing three plane geometric geoid surfaces. A total of 19 points were used in the study. The least squares adjustment technique was applied to compute the models’ parameters. Microsoft Excel programs were developed for the application of the models in the study area. The Root Mean Square Index was applied to compute the accuracy of the models. The three geometric geoid models were compared using their accuracy to determine which of them is most suitable for application in the study area. The comparison results show that the three models can be applied in the study area with more reliability, with greater confidence in model 2.

Establishment of local geometric geoid model for Busoga, Uganda

“…It also shows that geoid heights can be interpolated in the study area with an accuracy of 0.067m with the Multiquadratic geoid model. The accuracy achieved in this study is within the ones obtained in previous studies [4][5][6][7][8][9][10]. With an accuracy of less than 10cm for the recommended model, it is fit for applications like engineering feasibility studies, GIS topographic mapping, remote sensing land-cover mapping projects and oceanographic applications [24].…”

“…Oluyori et al [9] compared two polynomial geoid models (Model 1 and Model 2) for orthometric heights interpolation in FCT, Abuja, Nigeria and recommends Model 1 with an accuracy of 11cm for application in the study area. Kyamulesire et al [10] also determined the local geoid model of Kampala, Uganda by comparing three plane geometric geoid surfaces (Model 1, Model 2 and Model 3) and recommended the three models for application in the study area with more reliability, as well as greater confidence in model 2.…”

“…The European Improved Gravity model of the Earth by New techniques, EIGEN-6C4 [11,10] is a global geopotential model adopted for the conversion of ellipsoidal heights to orthometric heights in Uganda. It is well known that global geoid models best the entire globe but not areas, regions or countries.…”

“…A truncated model at a lower spherical harmonic degree was applied in Jinja, Uganda, an accuracy of 1.390m achieved is considered very low. Considering the low resolution of the global geoid model in the country, the local geoid model of Kampala which is the capital city of Uganda was determined using the geometric method [10]. Busoga is a sub-region of Uganda.…”