斜面災害の発生地点における土地条件分析を目的としたカラー空中写真データの画像解析手法

抄録

Japan is known as the disaster island, various types of disasters occur every year in different parts of our country. The scale of disaster ranges from large to small, and in some cases these can be analyzed from satellite data with high resolution, but in other case aerial color photographs are more suitable for some cases.
It is very important to establish disaster prevention measures in order to grasp land conditions under which a large scale slope hazards, such as a landslide may occur, namely to clarify the differences of land conditions at these risky areas. For this purpose, it is considered to utilize effectively aerial photographs taken befere and after the occurrence of landslide. Since the aerial photograph has geometric distortion, it is necessary to convert the aerial photograph into a digital image and to obtain an orthographic image by applying geometric correction. Furthermore, using the corrected image of land conditions, it is possible to analyze the specific features of land conditions of the area where slope hazard may occur by overlaying the two temporal images with the corresponding pixels. In this paper, the emphasis is placed on the image analysis method of aerial color photograph for the purpose of analyzing the difference of land conditions of the area where slope hazards occurred freouently.
To explain the image analysis method more clearly, we attempted to make analysis using aerial color photographs of Jizuki mountain in Nagano Prefecture taken before and after the landslide occurence which took place on July 26, 1985.