3 May 2015
The photos taken from the satellite constellation and made available for international institutions immediately after the first tremors have been used to make a "damage map" of the most affected areas
The image to the left, available in high definition attachment, shows the damage map for the region in Nepal that was hardest hit by the violent earthquake on 25 April. It was created using shots taken by the COSMO-SkyMed satellite constellation - within the frame of cooperation between ASI and NASA-JPL, on the request of international institutions immediately after the first tremors.
The map (40x50km), known as a Damage Proxy Map (DPM), covers the region around Kathmandu and was processed by the ARIA (Advanced Rapid Imaging and Analysis) team together with Caltech using SAR interferometric radar data from the COSMO-SkyMed satellite constellation.
The technique uses a prototype algorhythm that rapidly identifies natural or man-made changes on the earth's surface, with assessment criteria focussing on damage to urbanised areas.
When the radar passes over areas with little or no destruction, the pixels in the image are transparent, becoming more opaque the more damage is picked up, as well as changing from yellow to red according to the severity of the damage - red marks the most serious damage in city areas. The shots were taken on 29 April, and are compared to reference surveys taken on 24 November 2014.
The image to the right (available in high definition attachment) shows the map of the damage laid over a land map marking the position of the damaged buildings with red and purple dots, as identified by a preliminary damage assessment by NGA(National Geospatial-Intelligence Agency) and UNITAR-UNOSATin cooperation with US Geological Survey and theBasilicata University.
The images to the side show how the regions marked in red on the damage map match up to the damaged structures, shown by the collapsed buildings in the "post-event" image at the bottom.
The maps shown were handed out to rescuers in Nepal to provide help and support during the post-seismic phase.