Snow Depths Survey by Aerial Photographs

Abstract

The Hokuriku region was attacked by heavy snow fall in January, 1963 and aerial photographs of the whole region were taken by the Defence Forces of Japan for providing basic data to prevent snow disasters.Using these aerial photographs, we, the staff of Geographical Survey Institute, compiled the distribution maps of snow depth on a scale of 1 : 200, 000 representing the snow depth by progressive depth at 1 meter intervals. (see fig.)Snow depths at about 1, 300 points were measured by Zeiss stereotop on aerial photographs, where the snow surface could be observed close to the exposed ground such as near rivers, canals, roads, etc. in lowland areas and snow breaks, ridges etc, in mountainous areas.The distribution pattern of snow depth was delineated on the aerial photographs by photo-interpretation based on the measured points of snow depth.Snow depth distribution maps are useful for estimating of accumulated snow amount which is very important both for flood control and power generating works in snow melting season.