Object-based Image Analysis for Mapping Tsunami-affected Areas

The recent experiences in the 2004 Sumatra earthquake and tsunami showed the efficiency of remote sensing techniques in quick damage mapping and recovery efforts. A variety of satellite images at different resolutions provided different aspects of information about the affected zones. After remotely sensed images are acquired, choosing a suitable image analysis method is a critical requirement. This study develops an object-based image analysis method for mapping the tsunami-affected areas. Its basic idea is the combined analysis of spectral and morphological information in a multi-scale space. A concerned object class such as vegetation at a specific range of size can be extracted by observing its behavior across the multi-scale space. Tsunami-affected zones of Thailand are chosen for demonstrating the performance of this new method. Both medium resolution satellite images (ASTER) and high resolution satellite images (QuickBird) are used. Affected areas which are identified by stripped-away vegetated areas are clearly shown as the objects rather than fragmentary zones by the conventional methods. This output is ready-to-use for further damage assessment in a GIS environment. Speeding up the processing, testing on other types of disasters and areas, and sensitivity analysis should be carried out in further studies.