Merging two SAR images of the Nasca Plain

An interferometric coherence image derived from two scenes acquired by the ERS-2 satellite, first in 1997 and then in 1999. The bright regions in the image show where the two scenes are highly correlated, indicating that there has been very little change in the terrain surface during the 2 year interval between the acquisitions. The darker regions show where de-correlation has occurred over this period, highlighting possible problem areas where erosion may be taking place.

The Nasca pampa is the bright region of high coherence in the centre-right of the image flanked by the highly de-correlated river valleys. The dark linear features are roads and tracks. The areas of run-off are clearly visible cutting across the pampa from the Andean foothills on the right, as was also evidenced by the Proba image.