Study of wavelet analysis conditions and visualization methods suitable for extracting falling rock generation sources

Abstract

Wavelet analysis is a method for producing microtopographic maps from aerial laser scanning data. In this study, we investigated the setting of the scale factor (s) and a visualization method for the wavelet coefficients to extract geological features (exposed rocks, boulders, and small cliffs) that may function as a source of falling rocks. Grid data with a grid size of 0.5 m were used for the study, which were generated from aerial laser survey data and the results of the survey. A correlation between the specific height difference in the range of 1.0–3.0 m and the positive wavelet coefficient was determined. Consequently, based on these results and those of a study on simulated terrain, a visualization method for the wavelet coefficients was proposed. Herein, setting s = 1.0 and 0.5, it was shown that s = 0.5 was appropriate for identifying geological features that may be considered as sources of rockfall.