Options
Accuracy assessment of 3d models using close-range photogrammetry methods
Date Issued |
---|
2018 |
In the study, the DJI Phantom 4 Pro drone with a 1-inch 20-megapixel camera on-board was used to take images of the Balbieriskis St. Holy Virgin Mary Church. The drone was used due to its maneuverability to take images above and around the church. Over 400 images were taken within 1 hour. Agisoft PhotoScan photogrammetry software was used to conduct the image processing. For the alignment of the 3D model 10 GCPs of structure were measured using tacheometric measurements. The image alignment or reconstruction of the image acquisition starts with the automatic detection of characteristic points or feature points on each image. Thereafter, a feature matching is performed in order to relate each point with its counterpart in other images. The focal length and image size of each image are slightly adjusted during a maximum likelihood adjustment, which allows an iterative bundle adjustment and the estimation of a sparse point cloud. In this phase, the GCPs are assigned to each image and the scene will be aligned in an absolute 3D coordinate system. All clear images with sufficient overlap were included in the processing in order to generate a dense point cloud of the church. GCPs were applied to correct the scale and georeference the model...
UAVs have become a common tool in buildings research as they provide higher resolution images compared with satellite imagery. Research indicates that unmanned aerial vehicles (UAVs) can be used for low-altitude imaging and remote sensing of geospatial information. UAVs are being used for surveying buildings due to their affordability, reliability and ease-of -use. Recent developments in photogrammetry technology provide a simple and cost-effective method of generating relatively accurate 3D models from 2D images . The integrated use of different spatial data sources is essential for this project. Ground Control Points (GCP) were also acquired by topographic measurements, allowing the connection of different modelled features in the model, as well as the absolute positioning of the site. A total station and handheld GNSS receiver were used for these measurements.