Modelling local geoid undulations using unmanned aerial vehicles (UAVS): a case study of the Federal University of Technology, Akure, Nigeria

The study was aimed at developing a geoid model using Unmanned Aerial Vehicle (UAV) technology. To accomplish this, a UAV was deployed to capture imagery of the study area from a height of 150m, with a ground resolution of 4.19cm. A total of 3737 images were obtained, covering an area of 725.804 hectares. The existing ellipsoidal and orthometric heights were used to georeferenced the acquired images. For the analysis, 35 points were utilized, with 20 points designated as ground control points (GCPs) and the remaining 15 points as check points (CPs). Using the UAV-derived Digital Terrain Models (DTMs), a dataset comprising 18,492 points was generated for both ellipsoidal (h) and orthometric (H) heights. The differences between these heights, referred to as geoid heights (N), were calculated as N = h - H for all 18,492 points. These geoid heights were subsequently employed to generate a geoid model, including contour maps and 3D maps, of the study area. To assess the accuracy of the UAV-derived geoid heights, a root mean square error (RMSE) analysis was performed by comparing them with the existing geoid heights and was found to be 0.113 m. The scientific novelty and practical significance are in the development of a local geoid model of the study area with centimetre-level precision. Thus, the output of this study can be used for a wide range of applications, including land management, construction, and environmental impact assessments in the study area.