Abstract
The paper deals with the calibration of a non-metric digital camera Nikon EOS 6D with a 50 mm lens that could be adapted as a potential UAV sensor for the purposes of aerial inspections. The determination of the internal orientation parameters and the image errors of the non-metric digital camera involved self-calibration with Agisoft Metashape software solving the network of the images obtained from different test fields: a chessboard field, a professional laboratory field and a spatially diverse research area. The results of the control measurement for the examined object distance of 6 meters do not differ significantly. The RMSE from the control measurement for the second analyzed object distance of 15 meters was calculated on the basis of the internal orientation elements. The images from the laboratory field, the spatial test area and the chessboard field were used, and the obtained results amounted to 7.9, 9.9 and 11.5 mm, respectively. The conducted studies showed that in the case of very precise photogrammetric measurements performed by means of the Nikon EOS 6D camera equipped with a 50 mm lens, it is optimal to conduct calibration in a laboratory test field. The greatest RMSE errors were recorded for the control images with the elements of the internal camera orientation calculated on the basis of the chessboard area. The results of the experiments clearly show a relation between the accuracy of the Nikon EOS 6D camera calibrations and the percentage of the frame area filled with the test field. This explains why the weakest calibration results were obtained from the chessboard test field.
Highlights
The measurement methods based on properly processed digital images have become increasingly popular in recent years
It should be noted that the vast majority of currently used digital cameras in Unmanned Aerial Vehicles are non-metric ones, whose internal orientation elements are not known
The methodology of the study focused on the use of three types of test fields for calibration and included an attempt to assess the impact of the field type on the accuracy of the photogrammetric measurement
Summary
The measurement methods based on properly processed digital images have become increasingly popular in recent years. A growing tendency can be observed in the availability of Unmanned Aerial Vehicles (UAVs) as a new solution in the fast acquisition of digital images at lower altitudes. In the studies of Jung et al (2009, 2010) the Authors attempted to evaluate such a solution in the context of gathering spatial 3D information from urban areas together with the analysis of the accuracy of the used photogrammetric methods. The Authors suggest using UAVs to collect and update spatial information for small and dynamically changing areas, to create virtual maps of cities or to provide new information to GIS databases. In the studies of Berteška and Ruzgienė (2013), the Authors indicate the benefits of using the UAV technology for generating orthophotomaps and for creating DEM based on GCP collected from Internet sources. It should be noted that the vast majority of currently used digital cameras in Unmanned Aerial Vehicles are non-metric ones, whose internal orientation elements are not (fully) known
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