Road Damage Assessment from High Resolution Satellite Remote Sensing Imagery in Wenchuan Earthquake

The strong Wenchuan Earthquake causes serious damage to the road infrastructure,which has bad influence on the disaster-relief work after the earthquake.Therefore,it is very important to evaluate the damage loss of the road in the disaster area quickly and accurately,especially in the emergency time of disasters.This paper introduces a method to evaluate the damage of roads from satellite remote sensing images with high spatial resolution in Wenchuan earthquake of 8.0 magnitudes.The study uses twenty nine high resolution satellite remote sensing images after the earthquake,including EROS-B,QuickBird,SPOT-5,ALOS data etc.These images are all panchromatic data.The spatial resolution is at least 3 meters.The study area includes 20 counties in the damaged area of Wenchuan Earthquake.The terrain conditions are complex for all counties except several of the Chendu city.The study method includes three steps.First,remote sensing imagery is geometrically corrected.Meanwhile,clouds are eliminated by the threshold of high gray values.Second,road regions in high resolution remote sensing imagery are segmented by geographic information of road.Third,damaged roads are detection by the following steps.Each road is segmented by a fixed length interval into several segments.Then for each segment,grey and texture feature in a neighborhood window are calculated.According to the model of damaged road,grey and texture feature are used to identify damaged roads.At last,the result of damaged road detection is used to calculate assessment indexes including damage distribution and damage grade of each county.The grading standard is setted in three levels,which are severely damaged,moderately damaged and lightly damaged,according to the damage rate of national roads and provincial roads.The result shows that the earthquake affected road infrastructure in all the twenty counties of the study area.Six counties are severely damaged,including Wenchuan county and Beichuan county;three counties are moderately damaged;and eleven counties are lightly damaged.It is proved that,comparing the results of this study and the ground investigation data,the assessment method of this paper could get a quick and relatively accurate evaluated result of the damage loss of the roads in the disaster areas using the high resolution satellite remote sensing images.The damaged road assessment method is very useful and feasible in the serious situation,especially when we cannot get the ground investigation information.