Satellite-based damage mapping following the 2006 Indonesia earthquake - How accurate was it?

The Yogyakarta area in Indonesia suffered a devastating earthquake on 27May 2006. Therewas an immediate international response, and the International Charter “Space and Major Disasters” was activated, leading to a rapid production of image-based damage maps and other assistance. Most of the acquired imageswere processed byUNOSAT andDLR-ZKI, while substantial damagemapping also occurred on the ground. This paper assesses the accuracy and completeness of the damagemaps produced based on Charter data, using ground damage information collected during an extensive survey by Yogyakarta’s Gadjah Mada University in the weeks following the earthquake and that has recently become available. More than 54,000 buildings or their remains were surveyed, resulting in an exceptional validation database. The UNOSAT damage maps outlining clusters of severe damage are very accurate, while earlier, more detailed results underestimated damage and missed larger areas. Damage maps produced by DLR-ZKI, using a damage-grid approach, were found to underestimate the extent and severity of the devastation. Both mapping results also suffer from limited image coverage and extensive cloud contamination. The ground mapping gives a more accurate picture of the extent of the damage, but also illustrates the challenge of mapping a vast area. The paper concludes with a discussion on ways to improve Charter-based damage maps by integration of local knowledge, and to create a wider impact through generation of customised mapping products using web map services. © 2010 Elsevier B.V. All rights reserved.