UAV based Topographical mapping and accuracy assessment of Orthophoto using GCP

Abstract

For smaller locations, the traditional aerial photogrammetry techniques utilizing helicopters or airplanes are expensive and difficult. A new competitive strategy is necessary for quick spatial data collecting at a low cost and in a short amount of time for a developing nation like Nepal where geospatial data is in great demand. Currently, the UAV (Unmanned Aerial Vehicle) has become an alternative for different engineering applications, especially in surveying, one of these applications is for making a topographical map. This study demonstrates how this can be achieved using one of the evolving remote sensing technologies, Unmanned Aerial Vehicles (UAVs). Besides, this study also involves image processing and topographic map production using Pix4D and GIS environments. For this study,DJI Mavic Air-2 Advanced quadcopter collected about 207 images at a flying height of 80 m above the Kathmandu University area. An orthophoto of 2.4 cm GSD covering 127064 sq. Meter of area was produced. The RMSE of 5.37 cm in X and 3.32 cm in Y and 4.05cm in Z was achieved With appropriate checkpoints.The measurements in the orthophoto replicated the field measurements to an error of less than 0.5% of the actual dimensions.