Abstract
We used synthetic aperture radar (SAR) data collected over Peru’s Lines and Geoglyphs of the Nasca and Palpa World Heritage Site to detect and measure landscape disturbance threatening world-renowned archaeological features and ecosystems. We employed algorithms to calculate correlations between pairs of SAR returns, collected at different times, and generate correlation images. Landscape disturbances even on the scale of pedestrian travel are discernible in correlation images generated from airborne, L-band SAR. Correlation images derived from C-band SAR data collected by the European Space Agency’s Sentinel-1 satellites also provide detailed landscape change information. Because the two Sentinel-1 satellites together have a repeat pass interval that can be as short as six days, products derived from their data can not only provide information on the location and degree of ground disturbance, but also identify a time window of about one to three weeks during which disturbance must have occurred. For Sentinel-1, this does not depend on collecting data in fine-beam modes, which generally sacrifice the size of the area covered for a higher spatial resolution. We also report on pixel value stretching for a visual analysis of SAR data, quantitative assessment of landscape disturbance, and statistical testing for significant landscape change.
Highlights
C-band synthetic aperture radar (SAR) data gathered by the Sentinel-1 satellites, aiming to assess the utility of that data in results, we built upon our analysis of the UAVSAR data by applying a similar analytical process pursuing the kinds of monitoring tasks we had demonstrated with UAVSAR
To C-band SAR data gathered by the Sentinel-1 satellites, aiming to assess the utility of that data in Sentinel-1A, launched on 3 April 2014, carries a C-band SAR instrument that transmits and pursuing the kinds of monitoring tasksof weabout had demonstrated with receives radiation at wavelengths five centimeters
Our observations on the ground indicate that even small surface disturbances are visible as low volumes of water moving slowly across the ground surface, which was documented at the time of slightly decorrelated areas in the UAVSAR-derived correlation images
Summary
Recent years have seen a surge in interest in using satellite SAR data for research and the management of archaeological sites and landscapes. This is partly due to the profusion of SAR data being collected: satellite SAR instruments can cover much greater areas than airborne SAR, and satellite SAR can be obtained for, essentially, the entire world. In this project, we used data collected in Sentinel-1’s Interferometric Wide (IW) Swath mode, which covers a strip 250 km wide
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