DETECTION OF THE EARTHQUAKE DAMAGED BUILDINGS FROM POST-EVENT AERIAL PHOTOGRAPHS USING PERCEPTUAL GROUPING

摘要

The collapsed buildings due to Izmit, Turkey earthquake that occurred on 17 August 1999 were detected from post-event aerial photographs using the shadow analysis and the perceptual grouping procedure. The selected area of study is a part of the city of Golcuk, which is one of the urban areas most strongly hit by the earthquake. The area contains a total of 282 buildings, of which 79 are collapsed and 203 are un-collapsed. First, the Canny edge detector was applied to detect the edges between the cast shadows and the surroundings. Second, the output edge image was converted into vector line segments through a raster-to-vector conversion process. These line segments were then grouped together using a two-level hierarchical perceptual grouping procedure. The boundaries of the buildings were available and stored in a GIS as vector polygons. Therefore, after the perceptual grouping procedure, the damage conditions of the buildings were assessed on a building-by-building basis by measuring the aggreement between the detected line segments and the vector building boundaries. The results obtained is satisfactory. The overall accuracy was found to be 72.6percent. Of the total 79 collapsed buildings, 63 were detected correctly by the proposed approach, giving 79.7percent producer's accuracy.