High-resolution SAR coherent change detection in urban environment

Abstract

The identification of changes in urban settlements is of great interest for damage assessment after natural disasters, cadastral mapping and monitoring urban development and illegal activities. Radar-based remote sensing from space-borne platforms is quite useful in this scenario and Synthetic Aperture Radar (SAR) data is attractive due to its wide coverage, the day and night all-weather availability, and the sensitivity to slight changes in the scene structure. In this context, the launch of the European Space Agency (ESA) constellation Sentinel-1 has played a significant role: the exact repetition of the acquisition geometry, the repeated illumination and the sensitivity to centimetric changes thanks to the C-Band (5.4GHz) radar payload make Sentinel-1 the perfect instrument to monitor urban settlements. Coherent Change Detection (CCD) techniques are able to detect even the finest change in the structure of a target, so small to be comparable with the wavelength. This sensibility is an advantage, but turns into a drawback especially in an urban environment where every subtle change may cause an unwanted detection. This paper tackles the problem of the huge amount of triggered detections over urbanized areas with a combination of a high-resolution coherent multi-change detection technique and Geospatial Information System (GIS) post-processing. The final result is a map of buildings that are changed in the scene due to relevant variation of their structure. In this contribution, the complete workflow is explained, and a preliminary validation is carried out by means of a set of images gathered by Sentinel-1 and a set of optical images over the city of Manchester. .