The application of unmanned aircraft vehicle (UAV) to monitor construction area changes

Abstract

Recently, unmanned aerial vehicles (UAV) have been applied to various fields: mapping, aerial surveying, mine monitoring, construction monitoring, etc. UAVs have many advantages, such as high flexibility, low cost, and time savings, for each survey. This article studies a monitoring construction site project using photogrammetry images collected with a UAV Phantom 4 Pro. The study area was the Viet Phu Garden residential area in Phong Phu Commune, Binh Chanh District, Ho Chi Minh City. Due to the development of computer vision, photogrammetry was used to build 3D models. The study applied the structure-from-motion method to create point clouds, digital surface models (DSMs), and orthomosaics. The author monitored the area for six months (3 times of data collection) with Phantom 4 Pro using Agisoft Photoscan software to process and create products. We measured 28 points to make ground control points and checkpoints. The author proceeded to build orthomosaic and DSM 3 times to analyze changes in the area. The resolutions of the orthomosaic and DSM are 5.5 cm/pixel and 11 cm/pixel, respectively. We used checkpoints to evaluate horizontal and vertical errors. The root-mean-square error was less than 10 cm, which demonstrated the potential of UAVs for monitoring construction. We also used the DoD method to calculate the difference in DSM between each epoch. Then, we combined the DoD method with Orthomosaic to monitor the urban growth of the area. The results are divided into 2 main groups of changes, including changes in linear and regional form. Assessing the regional changes, the author divided 18 points into four main groups: New house, Completed house, House under construction, and other. Urban growth mainly occurred in the west and center of the study area. The results demonstrated that the use of the Phantom 4 Pro is appropriate for monitoring construction changes. The author recommended improving the quality of the results by combining them with the cadastral map to make planning and management easy.