The Influence of Image Properties on High-Detail SfM Photogrammetric Surveys of Complex Geometric Landforms: The Application of a Consumer-Grade UAV Camera in a Rock Glacier Survey

• Published in: Remote Sensing
• Main Authors: Martínez Fernández, Adrián, Serrano, Enrique, Pisabarro Pérez, Alfonso, Sánchez Fernández, Manuel, de Sanjosé, José Juan, Gómez Lende, Manuel, Rangel de Lázaro, Gizéh, Benito Calvo, Alfonso
• Other Authors: Analisis Geografico Regional, Facultad de Filosofia y Letras
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI 2022
• Subjects: Geografía; Geología; Unmanned Aerial Vehicle (UAV); Photogrammetry (SfM); Image format; Image properties; Mapping; Change detection; Geomorphology; Permafrost; 5404 Geografía Regional; 2506.01 Geología Regional; Atkinson; permafrost
• Online Access: https://hdl.handle.net/10612/22142; https://doi.org/10.3390/RS14153528

[EN] The detailed description of processing workflows in Structure from Motion (SfM) surveys using unmanned aerial vehicles (UAVs) is not common in geomorphological research. One of the aspects frequently overlooked in photogrammetric reconstruction is image characteristics. In this context, the present study aims to determine whether the format or properties (e.g., exposure, sharpening, lens corrections) of the images used in the SfM process can affect high-detail surveys of complex geometric landforms such as rock glaciers. For this purpose, images generated (DNG and JPEG) and derived (TIFF) from low-cost UAV systems widely used by the scientific community are applied. The case study is carried out through a comprehensive flight plan with ground control and differences among surveys are assessed visually and geometrically. Thus, geometric evaluation is based on 2.5D and 3D perspectives and a ground-based LiDAR benchmark. The results show that the lens profiles applied by some low-cost UAV cameras to the images can significantly alter the geometry among photo-reconstructions, to the extent that they can influence monitoring activities with variations of around ±5 cm in areas with close control and over ±20 cm (10 times the ground sample distance) on surfaces outside the ground control surroundings. The terrestrial position of the laser scanner measurements and the scene changing topography results in uneven surface sampling, which makes it challenging to determine which set of images best fit the LiDAR benchmark. Other effects of the image properties are found in minor variations scattered throughout the survey or modifications to the RGB values of the point clouds or orthomosaics, with no critical impact on geomorphological studies. SI We thank Viktor Kaufmann and the Institute of Geodesy of the Graz University of Technology for their assistance. We also thank Alan Atkinson, Ibai Rico, Eñaut Izagirre, and Isaac Gurdiel for technical and field support. This work could not have been accomplished without the ...