Videogrammetrie

The aim of the master thesis was to analyze the basic requirements for the use of video as a data source for photogrammetry. Three case studies were developed in the form of an experiment, where the subject of investigation was the resolution of the video, or the frames from it, and the frame rate of the video.
The first case study was developed in the physical-geographical domain. A UAV flight was performed in which images were taken using the photogrammetry method, followed by video recordings at the same exposure settings with video resolution settings of 4K and FHD and frame rates of 25 FPS and 50 FPS. Furthermore, a flight with an oblique camera was performed around the object of interest in a circle with 4K resolution at frame rates of 25 FPS and 50 FPS. The videos and photographs thus produced were processed in Agisoft Metashape Professional and the results compared with each other. During the work, it was found that the frame rate of 50 FPS at a moving speed of the drone of 1.8 m/s is too high and generates a large number of photos that cannot be subsequently processed. According to the results, it was found that at this speed at a flight height of 25 meters above the ground, the optimal frame rate is 8.3 FPS. It was also confirmed that higher resolution results in greater resolution on the ground. From a video taken with an oblique camera at 4K resolution, the same resolution on the ground can be achieved as a vertical camera flight at FHD resolution, and in much less time. To simplify post-processing, a Microsoft Excel calculator was created and is available on the thesis website.
The subject of the second case study was to test video acquisition on a small scale model in order to create a 3D model. The experiment was processed several times. Testing was carried out in laboratory conditions, keeping constant lighting conditions, the same speed and camera movement path. It was found that it is necessary to have sufficient illumination on the model and its surroundings for proper alignment of the images, and also that when the video is taken from a greater distance, fewer erroneous fragments are produced on the model. 4K and FHD resolutions were tested on the interchangeable lens camera. Frame rates of 25, 30 and 60 FPS at 4K and FHD were tested. According to the results, the lower frame rate, i.e. 25 FPS, is preferable, at which the resulting model has less amount of distorted areas.
The third case study was developed in the area of urban development. The field investigation was carried out twice and in neither case did it yield satisfactory results. The direction of camera movement was straight instead of moving in a circular path, which was probably the main reason for the misalignment of the captured video images. Nevertheless, the first field investigation of this case study was processed with subsequent comparison of results across different video settings. It was found that, even in this case, the 4K resolution video setting with a frame rate of 25 FPS yielded better results.
After processing the three case studies, it can be concluded that the video resolution has a significant impact on the appearance of the final image. At higher resolution, the resulting model and orthomosaic has a higher resolution, but it does not match the photographed images even at high frame rates. Furthermore, it has been confirmed that high frame rate has a negative effect on the final image. The use of low motion speed and high frame rate causes an excessive number of images, which leads to higher storage requirements and thus high processing effort. As the undesirable rolling shutter effect could not be observed in any of the captured images, this defect was not further investigated and tested. This was due to the low speed of movement and the direction of rotation of the camera.
As the main output, the processing procedure created is shown in the flow chart. Another output is a calculator created in Microsoft Excel, which makes it easier to select the appropriate equipment, video settings, flight height and other important parameters for determining longitudinal overlays. Furthermore, XML files were created that contain group processes with preset parameters for easier processing in Agisoft Metashape.