Development of estimation method for artificially modified terrain using airborne LiDAR

Abstract

In recent years, disasters in artificially modified terrain have been regarded as an issue. On the other hand, there are cases where rare ecosystems exist in such terrain. Therefore, authors attempted to estimate the artificially modified terrain. A study area was located in Tsuguro Highland, Okayama prefecture where traditional ironworks was operated. First, modified terrain with land use was extracted by interview from local people, ortho mosaic image and CS-3D-map made from airborne LiDAR. It was possible to interpret the paddy field and the iron sand mining site by the CS-3D-map. On the other hand, they could not be interpreted by ortho image. Therefore, it was possible to extract the artificial modified terrain with high accuracy by using both ortho image and CS-3D-map. Next, the artificially modified terrain was estimated by geometrically averaging the densities of gentle slopes and steep slopes created from DTM using LiDAR. Eight patterns of thresholds for gentle and steep slopes were set, and the deviation of the modified terrain estimation values in the artificially modified landform was tested by the χ² test. As a result, the estimated values were significantly deviated in all patterns. When the threshold of the gentle slope angle was 7.709° and the steep slope angle was 42.169°, the χ² value became the maximum. The modified terrain estimation value showed high in paddy fields, roads, and pastures, and low in the unmodified terrain. The accuracy of the extracted artificial modified terrain and the artificially modified terrain estimation value was confirmed by an error matrix, and the Kappa statistic was calculated. As a result, it was judged to be "moderate match". Therefore, it was clarified that the method developed in this study can estimate areas where artificially modified terrains are distributed.