THREE-DIMENSIONAL MODELLING WITH CLOSE RANGE PHOTOGRAMMETRY AND DIGITAL SURVEY METHOD FOR NEW ADMINISTRATIVE BUILDING IN FEDERAL SCHOOL OF SURVEYING OYO.

ABSTRACT The need for accurate three-dimensional (3D) modelling of high-rise structures is essential in modern surveying, engineering, and urban planning. This study focuses on generating a precise 3D model of the New Administrative Building of the Federal School of Surveying, Oyo, using a combination of close-range photogrammetrywith an unmanned aerial vehicle (UAV) and terrestrial surveying with a total station. The aim of the project was to create a reliable 3D model through the integration of both methods to enhance accuracy, completeness, and efficiency. The specific objectives were to establish and select control points, capture aerial images of the building using UAV photogrammetry, determine coordinates of selected points using a total station for accuracy assessment, process the images in AgisoftMetashape for georeferencing and 3D reconstruction, analyse the model’s accuracy through coordinate comparison, and evaluate the Root Mean Square Error (RMSE) of the generated model. The methodology involved UAV flight planning and automated image acquisition using aUAVdroneMavic2Pro, while terrestrial observations were carried out using a CHCNAV CTS-112R4 total station. Four Ground Control Points (GCPs) were established using GNSS in static mode for georeferencing. The RMSE method was applied to assess the discrepancies between photogrammetric and terrestrial coordinates. The results revealed that UAV photogrammetry provided rapid data acquisition and high-resolution imagery, whereas terrestrial surveying offered superior positional accuracy. The computed RMSE values of 0.0029 m in Easting, 0.1100 m in Northing, and 0.1323 m in Height confirmed that integrating both techniques significantly enhanced 3D model precision. Despite challenges such as long data processing time, limited computer capacity, and unfavourable weather conditions during UAV flights, the study concluded that combining UAV photogrammetry and terrestrial surveying providesacost-effective, accurate,andefficientapproachto3Dmodellingofhigh-risestructures. It is therefore recommended that future research incorporate LiDAR or hybrid UAV–TLS systems to achieve further improvements in model accuracy and precision.