LAUSR

Abstract The article presents the issue of the measurement of the repose angle (with respect to cones) and the methodology of its determination along with measurement uncertainty analysis, proposed by the authors. The measurements were performed in terrain conditions. The subject of research were 5 to 8-meter high cones made of the washed gravel of three different granule size ranges (0-2 mm, 8-16 mm, 32-60 mm). For the research purposes, two contemporary photogrammetric methods commonly used in 3D measurements were applied, i.e., terrestrial laser scanning (TLS) and Structure from Motion (SfM) technique based on digital images acquired with the use of an Unmanned Aerial Vehicle (UAV). The comparative analysis of the possible use of the TLS and UAV methods in the measurement of the angle of repose (strengths and weaknesses) was carried out and the simplified version of measurement was offered. The both methods produced very similar results, with measurement uncertainty falling within the range of 0.4-0.7 o . These results confirm the correctness of the taken measurements of large spatial objects and computational methods used to calculate the value of the angle of repose along with the level of measurement uncertainty.