The Synergistic Use of RADARSAT-2 Ascending and Descending Images to Improve Surface Water Detection Accuracy in Alberta, Canada

Large, e.g., provincial or national, scale near-real-time surface water monitoring is an ambitious task, which can be accomplished by using Synthetic Aperture Radar (SAR) satellite data. SAR has demonstrated the ability to distinguish water and land, but there are many common errors of commission and omission that arise due to the side-looking nature of SAR and due to some landcover types with similar backscatter like roads and pasture. A method is proposed to fix/mitigate these errors through the use of combined ascending/descending RADARSAT-2 image pairs and ancillary data. The results of a corrected water/land binary image were, on average, 99.4% accurate for the Boreal Forest Region (Utikuma) of Alberta, Canada, while for the Rocky Mountain Region (Westcastle) also in Alberta, the results proved to be 99.9% accurate when distinguishing water from land. These accuracies were achieved through the reduction of the water false positive rate and a slight reduction in the water true positive rate. These high accuracy values can be partially attributed to the relative low ratios of water to land in the study regions. We hope that these methods can be used and improved in order to move towards large scale dynamic surface water and wetland mapping.