Study on measurement and evaluation of land transformation using photogramtry and GIS

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As for the earthquake disaster in recent years in Japan, housing estates in the suburban area have been affected. These estates were developed in the hills by land transformation with fills in the valleys and cuts on the ridges. The purpose of this study is to measure the land transformation and to evaluate the land conditions of the land against earthquake, using photographic surveying and GIS. A series of analyses is developed from the preparation of the DEMs of the land before and after transformation, through formation of the land condition indices in GIS, to multivariate analysis to discuss the relationship between the housing damage and land conditions.In the case that large scale topographical maps are not available to obtain the DEM before land transformation, air photographs may be available. However, it was proved that direct DEM formation by digital photogrametry technology was difficult to obtain the DEM precisely by the pilot study. Instead, the DEM was obtained by a series of techniques : air photographs → stereoplotting contours → digitize the contours → DEM formation in GIS.Housing damages in the transformed land in Kushiro, Kobe and Fukuoka were analyzed by the series of the techniques. The relationship between the spatial distribution of earthquake damage (building damage) of each case and the various land condition indices were analyzed by the cross tabulation and logistic regression analysis.As a result, "thickness of fills" and "distance from cut-fill boundary line" were recognized influencing building damage as significant land conditions. Furthermore, the results of the cases studies are examined in order to predict future damage in the transformed land. The damage of Northern Miyagi earthquake which occurred in 2003 in the study period were investigated and considered, as well.