AscDAMs: advanced SLAM-based channel detection and mapping system

Abstract. Obtaining high-resolution, accurate channel topography and deposit conditions has been a challenge for the study of channelized debris flow. Currently, widely used mapping technologies including satellite imaging and drone photogrammetry struggle to precisely observe channel interior conditions of long and deep mountainous gullies, particularly those in the Wenchuan earthquake region. SLAM is an emerging tech for 3D mapping; however, extremely rugged environment in long and deep gullies poses two major challenges even for the state-of-the-art SLAM: (1) atypical features and (2) violent swaying and oscillation of sensors. These issues result in large deviation and lots of noise for SLAM results. To improve SLAM mapping in such environments, we propose an advanced SLAM-based channel detection and mapping system, namely AscDAMs. It features three main enhancements to post-process SLAM results: (1) the digital orthophoto map-aided deviation correction algorithm greatly eliminates the systematic error; (2) the point cloud smoothing algorithm substantially diminishes noise; (3) the cross-section extraction algorithm enables the quantitative assessment of channel deposits and their changes. Two field experiments were conducted in Chutou gully, Wenchuan County in China in February and November 2023, representing observations before and after the rainy season. We demonstrate the capability of AscDAMs to greatly improve SLAM results, promoting SLAM for mapping the specially challenging environment. The proposed method compensates for the insufficiencies of existing technologies in detecting debris flow channel interiors including detailed channel morphology, erosion patterns, deposit distinction, volume estimation and change detection. It serves to enhance the study of full-scale debris flow mechanisms, long-term post-seismic evolution, and hazard assessment.