Validation and calibration of Canada-wide coarse-resolution satellite burned-area maps

Satellite-based mapping can provide a timely and efficient means of identifying burned vegetation at continental scales for estimating greenhouse gas emissions and impacts on the terrestrial carbon budget. In this study, we used a sample of 55 Landsat Thematic Mapper (TM) scenes distributed across Canada to validate and calibrate 1998 and 1999 national-level burned areas maps produced using coarse resolution (approx. 1-km) SPOT VEGETATION and NOAA AVHRR imagery. Commission and omissions errors, based on fire events greater than 200 ha, were found to be small in the coarse resolution maps (4 percent and 1 percent, respectively). However, the course resolution burned-area estimates were 72 percent larger than the crown fire burned area mapped at 30 m using Landsat TM (11,039 versus 6,403 ha average area). This bias was attributed to spatial aggregation effects in which the coarse resolution product included the tree crown fire, partial burn, and unburned fractions of a pixel. A regression calibration model (R-2 = 0.95, p < 0.0005, RMSE = 3,015 ha, n = 155) based on a VGT/TM double sampling approach was derived to correct for the aggregation bias and to provide Canada-wide estimates of crown fire burned area.