GISdevelopment.net ---> AARS ---> ACRS 1992 ---> Forestry Use of Photogrammetry for Researching of The Distribution of Damage from a Tornado Ichiro Adachi, Toshio Koizumi Koutchi, Tada Department of Civil Engineering Chiba Institute of Technology 2-17-1 Tsudanuma, Chiba, Japan Abstract This distribution of damage from a tornado which struck Mobara city in Chiba Prefecture, Japan on December 11, 1990 was researched by using photogrammetry. We provided two scenes of aerial photograph at the damaged are in Mobara city, one was before the tornado and another after the tornado. The number of houses completely destroyed were 80, houses partly destroyed 156, and houses with roof tiles blown off 1,489. These damage were confirmed by the way of fielded investigation. Photogrammetry is useful for such as damage investigation, but has a weak point that everything being out of sight from the upper air can not take a photograph. Outline of Damage Investigation Regarding a Tornado Mobara city is to around 60km east of Tokyo, and the urban district area in the city which was damaged from a tornado is on the southern tip of the Kujuukuri Plain of Chiba Prefecture and on a distance of around 10km to the Pacific Ocean. Kujuukuri Plain is bounded by small hills on the west and south. A tornado occurred on December 11th, 1990, around 19:15 by the side of small river on the southern part of Mobara urban district, and passed through a national road toward the north in about 60km an hour. Damaged area is 3.5km long by 0.5 ~ 1.0 km wide. The investigation of damage to structures in the field was undertaken for three days from December 13th. The method of investigation was that damaged area was falled into four divisions with reference to damage data of municipal government, every houses and constructions were the subject of investigation, and every data were filled up in a prescribed form, besides photographs were taken by the four sides of house. Photogrammetry was used for investigation of damage in the pathway of a tornado on December 15th by the cooperation from KOKUSAI KOGYO which is the big company of photogrammetry in Japan. Aerial photographs before the damage in a same area were offered by KEIYOW SURVEYING COMPANY. Investigation by Photogrammetry In the damaged area, it was can object of study to grasp the whole existing state of things and the pathway of a tornado, therefore photogrammetry was used to be adopted to authors need. Fig. 1 shows an index map of aerial photograph along the pathway of a tornado. Circular marks in the fig. 1 are center of lens of camera. Fig. 1 An index map of aerial photography in mobara city Fig. 3 Shows an aerial photograph in TAKASHI region where was extremely damaged from a tornado. This aerial photographs was taken after damaged. Key for photo-interpretation was provided as table 1. This table was used mainly for investigation of damages houses. Fig. 2 After a Tornado Fig. 3 before a Tarnado TABLE 1 Key for Photo-interpretation Address Photo-interpretation Identification 1 A. House is seen on both photograph B. House is not seen after tornado C. Being impossible of judgement Go-to address 2 Go-to address 3 Unclear 2 A. Completely destroyed B. Party destroyed C. Structure is not damaged D. Being impossible of judgement Completely Partly Go-to address 4 Unclear 3 A. Foundation is left over B. Being impossible of judgement Completely Unclear 4 A. Color of roof is partly renewed B. Pointed white plaster at the edge of blue sheet on the roof C. Color of roof is not renewed D. Being impossible of judgement Roof tilles blown off Roof tilles blown off Unclear Unclear Fig. 4 An Distribution of damage in Mobara City Results and Investigation The distribution of damage is showed in fig. 4. This map was obtained from photogrammetry and confirming by field surveying. Circular marks show completely destroyed, square marks now partly destroyed and triangular marks show houses with roof tiles blown off. Arrows show the direction of fallen trees. In these investigation, the followings are obtained. Completely destroyed houses have a tendence to be in a very limited area. And the area is scattered. Partly destroyed houses and houses with tiles blown off were confirmed. The pathway of a tornado, and fallen trees and telegraph poles, were confirmed. It was able to specify the damaged area in Mobara city.