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Spanish forest fire aftermath surveyed by Envisat

The damage done to Spain’s Guadalajara province by July’s fierce forest fire has been measured from space by Envisat. The four-day blaze began on 16 July, when a barbecue in pine woodland went out of control, spread by strong winds across a very dry landscape. Eleven volunteer firefighters died tackling the blaze, which at its height threatened to engulf the nearby villages of Selas and Ablanque. Firefighters succeeded in creating a fire-break to stop its spread, backed up by water-bombing aircraft. As the Spanish authorities assess the fire’s aftermath, a rapid damage estimate has been performed using Envisat’s Medium Resolution Imaging Spectrometer (MERIS) instrument.

A 24 July MERIS Full Resolution mode image with a spatial resolution of 300 metres was processed to reveal burned areas by a team led by Dr. Federico González-Alonso, head of the Madrid-based Laboratorio de Teledetección (Remote-sensing Laboratory) of the Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (National Institute for Agriculture, Food Research and Technology or INIA). “MERIS measures the solar radiation reflected by the Earth in 15 selectable spectral bands in the visible and near infra-red,” explained González-Alonso. “We utilised bands that were particularly sensitive to vegetation, then performed an automatic matched filtering analysis on the stacked bands to designate ‘endmembers’ – spectrally pure areas that could be visually classified as very burnt. The file obtained was reclassified by modifying the histogram or graphical bar used, so pixels with values over 0.3 were considered burnt. The resulting perimeter gives us a burnt area estimate of 11 313 hectares.” This figure compares well to forest fire burnt area estimates from other sources of 12 000 hectares.