Comparative Study of UAV LiDAR, Terrestrial Laser Scanner, and iPhone 15 Pro LiDAR in Rock Discontinuities Characterization for Rockfall Analysis

The characterization of discontinuities in rock slopes has traditionally been a time-consuming and expensive endeavor, the physical mapping itself involves extended stages as engineering geologists document key characteristics of the slope's discontinuities. Analyzing these discontinuities and determining their orientations are crucial for assessing the overall stability of a rock mass. However, recent advancements in remote sensing techniques such as UAV LiDAR, Terrestrial Laser Scanning (TLS) and iPhone 15 Pro LiDAR have revolutionized this process. Now, it is possible to remotely collect highly detailed point cloud data of a rock slope within a few hours and at significantly safe environment. These methods yield 3D point clouds and high-resolution images of rock outcrops, enabling the creation of three-dimensional reconstructions. The availability of such data has created new opportunities for collecting and assessing information about discontinuity characteristics, particularly geometric properties such as dip, dip direction, spacing, and persistence of joints in a rock slope. This paper presents a comprehensive review on capabilities of respective approach to characterize discontinuities on a rock slope, along with limitations and the advantages. In this study, several representative rock slopes underwent surveys using various techniques, including TLS, UAV LiDAR, and iPhone 15 Pro LiDAR. A comparative analysis of the results was conducted to determine the effectiveness of these new digital surveying and analysis approaches. The results of the study demonstrate better characterization of discontinuities by TLS with minor setbacks such occlusion and orientation bias during data collection. UAV LiDAR information provides comprehensive coverage of the rock outcrop with fewer point cloud density, while the LiDAR data acquisition from iPhone 15 Pro is limited to a specific distance from the rock slope. Indeed, the integration of these three approaches provides more inclusive analysis and characterization of rock discontinuities as each method compliments one another in terms of strength and limitation in characterizing rock slopes at various scales.