Abstract
Rapid development and growing availability of Unmanned Aerial Vehicles (UAV) translates into their more wide-spread application in monitoring of the natural environment. Moreover, advances in computer analysis techniques allow the imaging performed with UAVs to be used in creating Digital Elevation Models (DEM) and Digital Surface Models (DSM). DEMs are often employed in studies on geology, environment, engineering, and architecture. The presented paper discusses the procedures enabling the making of a precise DEM, discusses the aerial imaging data processing technique as well as determines the accuracy of obtained products in comparison with an existing Digital Elevation Model. Based on available literature the author indicates four sets of input parameters applicable in UAV imaging. Data collection missions were performed on two separate days in the area of a small peatland located in the Tuchola Pinewood, Poland. The study aims to address two research issues. Firstly, the author investigates the possibility of creating a DSM based on UAV imaging performed under unfavorable conditions and indicates whether results obtained via this method display sufficient quality to be seen as an alternative to the traditional surveying techniques (LiDAR). Secondly, the article determines the input parameters for a photogrammetric flight that ensure the highest accuracy of a resulting DSM. The analyses show a strong positive correlation between the DSMs prepared based on UAV imaging with data obtained by means of traditional methods (LiDAR). Mean correlation coefficient ranged from 0.45 to 0.75 depending on the type of land use and input parameters selected for a given flight. Furthermore, the analysis revealed that DSMs prepared based on UAV imaging—provided the most suitable input parameters are selected—can be a viable alternative to standard measurements, with the added benefit of low cost and the capacity for repeatable data collection in time. Admittedly, the method in question cannot be utilized in relation to peatlands overgrown with high vegetation (trees, shrubs) as it effectively diminishes the accuracy of obtained DSMs.
Highlights
Studies conducted on a small to medium scale require highly accurate data pertaining to the elevation of terrain
The study compares Digital Surface Models (DSM) generated based on Unmanned Aerial Vehicles (UAV) flights with DSM data from laser scanning performed in the same area to determine the correlation between data sets, and assess their usefulness
The analyses show that both on the first (16.08.2021) and the second date (30.10.2021) of flight passes the best results were obtained when utilizing settings selected for DSM 2 (Table 1, DSM 2—overlap: 70, altitude: 35 m, camera angle: 60°), which constitute the default settings recommended by the developer of Pix4D software
Summary
Studies conducted on a small to medium scale require highly accurate data pertaining to the elevation of terrain. It is an imperative for determining precise location and elevation of objects both at the stage of preparation and conduct of research. Owing to the development of technology and its increasing availability, Unmanned Aerial Vehicles (UAV) have become a viable option for establishing precise DEMs in relation to relatively vast areas and at very low cost (Moore et al, 1991; Walker and Willgoose, 1999; Thar and Ahmad, 2013; Audronis, 2015; Uysal et al, 2015; Akbari et al, 2016; Martínez-Carricondo et al, 2018; Zmarz et al, 2018; Ajibola et al, 2019; Akturk and Altunel, 2019; Donager et al, 2021; La Salandra et al, 2021; Sankey et al, 2021; Vavulin et al, 2021; Villoslada Peciña et al, 2021). Over the past several years low-altitude photogrammetry (Kędzierski et al, 2014) has become one of the main methods of generating DEMs
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