Amplitude change detection with ENVISAT ASAR to image the cultural landscape of the Nasca Region, Peru

Synthetic aperture radar (SAR) amplitude information from ENVISAT C-band advanced SAR (ASAR) data was used to analyse the cultural landscape of the Nasca region, southern Peru. A multispatial environmental analysis was performed over the whole drainage basin of the Rio Grande, by extracting the radar backscattering coefficient (σ0) of both natural and anthropogenic features between 2003 and 2005. Co-registration of the ASAR scenes to a single master resulted in precisions of less than 0.1 pixels along both the range and azimuth directions. Four different products were generated based on the co-registered ASAR stack: (i) temporally averaged radar signatures of the targets between 2003 and 2005; (ii) time series of spatially averaged radar signatures within selected areas of interest; (iii) amplitude change detection products based on (iii) image ratios and (iv) RGB colour composites between different scenes. Comparisons of annual and seasonal records through amplitude change detection maps highlighted σ0 changes over the floodplains of the Rio Ingenio and Rio Nazca, which correlate well with evidence from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data acquired in 2003, 2004 and 2007. Inferences about land use and soil conditions were retrieved from the σ0 change patterns, thereby proving the capability of this approach to support landscape evolution studies, even with SAR imagery of medium resolution (~30 m). Our results also demonstrated actual potential for monitoring mass movements and land surface processes, to assess the susceptibility of archaeological heritage and cultural landscape to natural hazards