Mapping forest disturbance using long time series of Sentinel-1 data: Case studies over boreal and tropical forests

Clear-cutting and logging operations are the most drastic and wide-spread changes that affects the hydrological and carbon-balance properties of forested areas. A long time series of Sentinel-1 images are used to study the potential for mapping logged areas in areas in boreal zone region and in tropical forest. In the first case study in southern Finland, the time series covered a full year starting in October 2014, in 200km-by-200-km study site. The Sentinel-1 images were acquired in Interferometric Wide-swath (IW), dualpolarized mode (VV+VH). All scenes were acquired in the same orbit configuration. In the second case study the potential of Sentinel-1 time series for mapping logged areas was studied over tropical forest in Mexico. Acquisitions were made in the time frame between November 2014 and September 2015. The temporal behavior of the C-band backscatter was studied for areas representing: 1) areas clear-cut during the acquisition of the Sentinel-1 time-series, 2) areas remaining forest during the acquisition of the Sentinel-1 time-series, and 3) areas that had been clear-cut before the acquisition of the Sentinel-1 time-series. Algorithms for mapping the spatial extent of logged areas were developed and tested, showing potential of long time series of Sentinel-1 data for successful delineation of clear-cuts despite high sensitivity to seasonal and weather conditions.