Investigating RADARSAT-2 as a tool for monitoring grassland in western Canada

Abstract

Native grasslands play an important role in ecosystem function, biodiversity, climate change, and economics, yet quantifiable estimates of the rate and location of native grassland change in western Canada are not readily available. To date, optical remote sensing has been explored for grassland mapping, but cloud cover limits the availability of timely data for the discrimination of improved, as opposed to native, grassland. In this study we investigated the utility of RADARSAT-2 polarimetric imagery to map native grassland, improved grassland, and agricultural crops. Fine quad-polarisation mode RADARSAT-2 data were acquired at two incidence angles over a test site in southern Alberta every 24 days from 1 April to 31 October 2009 and were processed using the Freeman–Durden decomposition. Double-bounce, volumetric, and surface scattering properties suggest that native grasslands can be distinguished from cultivated cropping, especially using a mid- to late-season image. However, discriminating native grasslands from improved grasslands was more difficult. Land cover classification of a single RADARSAT-2 image from July 2009 provided reasonable but slightly less accurate results compared with a single Landsat-5 Thematic Mapper image (Kappa value of 0.65 compared with 0.81).