Multitemporal land cover mapping for Canada: methodology and products

A mapping methodology is presented for generating a land cover time series from coarse spatial resolution earth observation data. Historically, this has been a difficult task because of inconsistencies that can arise between maps due to inherent noise present in satellite observations. The new methodology reduces the inconsistency by incorporating several information sources unique to the presented approach of updating an existing land cover map backward and forward in time. It consists of change detection and a local evidence classification decision rule that incorporates the local spectral similarity for each class, local land cover proportions, and expected class changes based on the previous class and change direction. The methodology has been implemented to produce land cover maps of Canada for 1985, 1990, 1995, and 2000 from data acquired by the series of National Oceanic and Atmospheric Administration (NOAA) – advanced high-resolution radiometer (AVHRR) sensors. Accuracy assessment based on medium-resolution (30 m) reference data shows that land cover data produced with this new approach have an overall accuracy similar to that of other 1 km resolution land cover maps of Canada, but this product maintains high consistency between years, with a thematic resolution of 12 classes. An analysis of spatial and temporal patterns of land cover disturbances demonstrates the potential application of the multitemporal land cover time series.