10:45 〜 11:00
[HTT13-01] Measurement of microtopographical features using the low-cost mobile laser scanner in Nippara Limestone Cave, eastern Japan
キーワード：低価格モバイルレーザ測量、点群解析、溶食ノッチ、日原鍾乳洞
Understanding the landform development and corrosion process of limestone caves requires the measurement of the microtopography inside them. Qualitative descriptions would traditionally have been based on photographs and sketches. In recent years, photogrammetry and laser scanning have been widely spread and utilized for obtaining high-definition topographic data. Laser scanners are particularly becoming easily available for their lowering price. SLAM technology has enabled automatically combined point clouds, simplifying the creation of 3D topographic maps. Therefore, this study attempted 3D surveying the cave interior using a low-cost laser scanner at Nippara Limestone Cave in Tokyo, eastern Japan. The cave has a total length of 1,270 m and a height difference of 134 m and is open to tourists. The planform of the cave is constrained by faults, which developed with the branch points facing almost directly at right angles to each other. The measurement result showed the cave has various microtopographic features, including speleothems and corrosion notches. The three-dimensional topography of the cave was measured with a low-cost laser scanner, Avia (Livox, Inc.), and a laptop PC with SLAM installed. A total of 24 measurements obtained the overall shape of the cave. Cross-sections can be drawn at any location using CloudCompare, a free point cloud analysis software. The measurement result indicated corrosion notches of the hollow smaller than the ones noted in the previous study (Fig. 1). The processes of lateral erosion caused by groundwater convection and water flow are expected to be clarified by high-precision measurements of corrosion notch depths.