Abstract
The fully automated Structure-from-Motion approach for developing digital elevation models and orthomosaics has been known and used in photogrammetry for at least 15 years. Years of practice and experience have allowed researchers to provide a solid description of the applicability and limitations of this method. That being said, the impact of input processing parameters in software on the quality of photogrammetric products has yet to be fully ascertained empirically. This study is aimed at identifying the most advantageous processing workflow to fill this research gap by testing 375 different setup variations in the Agisoft Metashape software for the same set of images acquired using an unmanned aerial vehicle in a proglacial area. The purpose of the experiment was to determine three workflows: (1) the fastest, which has the shortest calculation time; (2) the best quality, which is as accurate as possible, regardless of the time taken for the calculations; and (3) the optimal, which is a compromise between accuracy and calculation time. Each of the 375 processing setup variations was assessed based on final product accuracy, i.e., orthomosaics and digital elevation models. The three workflows were selected based on calculating the height differences between the digital elevation models and the control points that did not participate in their georeferencing. The analyses of the root mean square errors (RMSE) and standard deviations indicate that excluding some of the optimization parameters during the camera optimization stage results in high RMSE and an increase in the values of standard deviation errors. Furthermore, it was shown that increasing the detail of individual processing steps in software does not always positively affect the accuracy of the resulting models. The experiment resulted in the development of three different workflows in the form of Python scripts for Agisoft Metashape software, which will help users to process image sets efficiently in the context of earth surface dynamics studies.
Highlights
The aim of this study was to investigate the influence of particular calculation parameters in the Agisoft Metashape software on the accuracy of photogrammetric products: digital elevation model (DEM) and orthomosaics
75 unsuccessful number remaining after filtration offor sparse first unsuccessful projects—the number of points remaining after filtration of sparse point clouds at this level (~600 points for all 75 chunks) was insufficient
Higher values in the order of 9, 15 or 44 cm were recorded where the level of accuracy was set to high or highest, the sparse point cloud was not optimized with the k3, k4, p1, and p2 parameters (“E” optimization parameter set), and no point limits were introduced in the sparse cloud
Summary
The relief of the Earth’s surface is constantly modified by natural processes (e.g., erosion, weathering) and direct human activity. These dynamics are important to studies of the landscape evolution as well as studies of processes which may pose threats to human life and infrastructure. Landscape dynamics have been studied in a number of contexts that include the following: (a) the possibility of the occurrence of landslides and areas susceptible to their formation [1–3]; (b) to observe areas at risk of snow avalanches [4];. (c) to monitor land surface changes due to mining activities [5,6]; and (d) to assess the dynamics of aeolian processes [7] or changes to riverscapes [8–12]. One example of areas characterized by high dynamics of the surface is proglacial areas [13–17]. Ongoing climate warming [18–20], characterized by an increase in mean annual air temperatures
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