The Effect of Ground Control Points Located on Roofs on Building Facade Accuracy

Abstract

The popularity of Unmanned Aerial Vehicle (UAV) photogrammetry is growing worldwide due to its low-cost advantage in collecting high-resolution 3D topographic models. This research aims to ascertain the impact of Ground Control Points (GCPs) located on building roofs on facade accuracy. A UAV survey covering 10.37 hectares was conducted to achieve this goal. The research utilised 91 GCPs for geo-referencing, with 38 on the ground and 53 on the roofs of the buildings in the area. Images were obtained with three different flight patterns: single (S), double (D), and circular (C), which represent flight routes. The images acquired from the flights have been subjected to two distinct GCP configurations, and two models were obtained for each flight pattern. The point cloud produced by a robotic total station was used to ensure the accuracy of the facades of the buildings in the models. The standard deviation (std. dev.) of the distances between the points on the facade and the reference planes (RPs) were used as a measure of accuracy. The std. dev. values of the model facades were compared by each other while considering the number of points of the surfaces. Average std. dev. values of the models fluctuate within a range of 7 to 11 cm.