Study of a method for extracting small-scale topographic irregularities using wavelet analysis maps

Microtopography and topographic parameter maps created from aerial laser profiler (LP) survey data are increasingly being used for business purposes. Wavelet analysis maps, unlike slope gradation maps, can be used to extract topographic irregularities without being affected by slope inclinations. First, a simulated terrain was created by changing the slope and the size of steps, and the size of steps that can be represented by a wavelet analysis map and by a slope gradation map was examined. Next, we examined the size of steps that can be extracted from the wavelet analysis and the slope gradation map for a slope with an average value of approximately 40 degrees, including the source of falling rocks, by using the results of the field survey. The size of the steps that can be extracted from the wavelet analysis map is approximately 2 m, and with the slope gradation map, it is more than 4 m. Hence, the wavelet analysis map is more accurate than the slope gradation map. Therefore, the wavelet analysis map can be used to extract smaller steps than those obtained with the slope gradation map.