In this monthly feature, we span the globe to examine Our Changing Landscape with time series of medium resolution RapidEye satellite imagery. The RapidEye archive dates back to late 2008 and already contains more than 3 billion square kilometers of data. This month, we travel to the war-torn nation of Syria and look at damage from bombs in the north-western city of Aleppo.
The RapidEye Constellation
RapidEye is a constellation of five 5-meter medium resolution satellites each offering five spectral bands of information. The RapidEye constellation offers a daily revisit time to every location on the planet with a huge footprint that is 77-km wide. The data is priced competitively with a base price of $1.28 per square kilometer for all five spectral bands – academics receive a discount on this price. RapidEye adds a fifth band, the red edge, to the ‘traditional’ multispectral set of blue, green, red and near-infrared (NIR). The additional spectral data available in the red edge band allows users to extract more useful land ‘information’ than can be from traditional 4-band imagery sources. When RapidEye imagery is ordered as a Level 3A Orthorectified product, images from multiple dates are extremely well registered, making it the ideal data source for Our Changing Landscape.
Significant Shelling in Aleppo, Syria
Many of us know the tale of the on-going conflict in Syria better than any summary I can offer here. As such, the point of this short piece is to show how 5-meter RapidEye imagery can be used to identify sites in Syria that have been bombed since the conflict began in March 2011. Since that time, the conflict has claimed the lives of an estimated 30,000 people or more with the northern town of Aleppo seeing significant fighting, especially since July 2012. Aleppo is one of the largest towns in Syria with a population of 2,132,000 (according to a 2004 census) and is hence an important geography to control. The forces of President Bashar al-Assad have riddled the landscape surrounding Aleppo with artillery shells in an attempt to dislodge the rebels. The RapidEye images that follow show just how significant the shelling of the rebels’ positions has been.
In order to complete this analysis, we used ‘training’ datasets (so to speak) to target our visual analysis. We used this piece from NBC News to help zoom in on the general location of the heaviest bombing around Aleppo. Once we were in the correct location, it was quite easy to locate the suspected impact craters. To assist with the visual analysis, we used a RGB composite display of the near infrared (NIR), red edge and red bands respectively which made the craters more apparent. We tried several supervised techniques to automate the detection of suspected locations but these attempts failed as the filters seemed to identify bare soil, not just impact craters. More advanced object oriented classification techniques may be able to identify the craters in an automated fashion, but were outside the scope of this exploratory piece. Either way, we think the following animation speaks volumes about the intensity of this Civil War.
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