MONITORING OF WILDFIRES IN BOREAL FORESTS USING LARGE-AREA AVHRR NDVICOMPOSITE IMAGE DATA

Normalized difference vegetation index (NDVI) composite image data, pr oduced from AVHRR data collected in 1990, were evaluated for locating and mapping the areal extent of wildfires in the boreal forests of Ala ska during that year. A technique was developed to map forest fire bou ndaries by subtracting a late-summer AVHRR NDVI image from an early su mmer scene. The locations and boundaries of wildfires within the inter ior region of Alaska were obtained from the Alaska Fire Service, and c ompared to the AVHRR-derived fire-boundary map. It was found that AVHR R detected 89.5% of all fires with sizes greater than' 2000 ha with no false alarms and that, for most cases, the general shape of the fire boundary detected by AVHRR matched those mapped by field observers. Ho wever, the total area contained within the fire boundaries mapped by A VHRR were only 61% of those mapped by the field observers. However, th e AVHRR data used in this study did not span the entire time period du ring which fires occurred, and it is believed the areal estimates coul d be improved significantly if an expanded AVHRR data set were used.