18 February 2009

TerraSAR-X over Victoria Bushfires

Imagery over fires is being donated by Apogee and our associates to assist the firefighters in Victoria

Apogee has tasked the new generation Radar satellite TerraSAR-X to acquire data over the severe bushfires in Victoria. This satellite can image an area twice a day through clouds and smoke at high resolution, where data acquired from the numerous optical satellites can not be captured until clouds part. The MODIS image shown below was acquired on the same day as the TerraSAR image showing the cloud cover at the time.

MODIS image from the 11th of February 2009.

Observation of the bushfires was made difficult due to extensive cloud cover as shown in the MODIS image above.

A ScanSAR image was acquired on the 11th of February 2009 and a composite image has been produced by merging a second ScanSAR image from the extensive archive TSX is capturing as a continuous background mission.

Comparing the post-fire acquisition to the archive data from the 20th of April 2008 improves the extraction of relevant information on fire impact.

A ScanSAR image has been acquired on the 11th of February 2009 and a composite image has been processed with archive data from the 20th of April 2008 to assess changes before and after the disaster. Changes can be seen in red. Slopes facing the radar sensor are brighter than the back slope of hills. This characteristic is enhanced due to lower leaf density in areas of forest where tree canopy has burnt.

The above picture is an extract of this image composition over the town of Marysville in which most of the infrastructures have been destroyed by the fire. The post-fire data registers a significant increase in backscatter magnitude compared to the archive data where houses have been destroyed due to the spread of debris and defoliation. This appears as distinct red areas within the township.

The town of Buxton in comparison, which has escaped the same level of destruction, is clearly distinguished by houses appearing white and indicating that their recorded radar reflection is unaltered from the previous year’s acquisition. This example shows how powerful the use of TerraSAR-X can be when no other visual assessment of the situation is possible due to heavy smoke and clouds.

The above image shows the Bunyip State park seen through clouds and smoke. The bright red area shows extensively burnt forest caused by the increased backscatter post-fire. This is due to the absence of leafs allowing the radar signal to interact with the bare ground and stems of the trees. On the slopes facing away from the radar signal this effect is not as evident.