Forests are crucial for the well-being of humanity, and the need to map and monitor their extent and condition in a timely fashion at local, national, regional and global scales is growing increasingly urgent. However, forests are very complex and difficult biomes to classify and map, even conventionally (eco-floristically). Because of the urgent need to map forest extent and condition, several organisations have turned to remote-sensing methods from which to derive their information. And because the areas that need to be mapped are typically large, many have turned to coarse spatial resolution data obtained from sensors flown onboard polar-orbiting satellites. In this paper we will review the use of coarse spatial resolution data from the U.S. National Oceanic and Atmospheric Administration's (NOAA) Advanced Very High Resolution Radiometer (AVHRR) sensor in studies of forest mapping and monitoring.
Although specifically designed for meteorological applications, data from the NOAA-AVHRR in their various forms, have also been widely used for a variety of land applications, for example crop monitoring in the Nile Delta (Tucker et. al., 1984a), grassland monitoring in Senegal (Tucker et. al., 1983) and the Sahel (Prince et. al., 1990), continental or global-scale vegetation classification (Townshend et. al., 1991), forest and bush fire mapping and monitoring (Gregoire, 1995), and tropical deforestation monitoring in South East Asia and South America (Malingreau et. al.,1989).
Among the reasons cited for their use in land applications are:
For the forest mapping and monitoring over large areas at national or regional scales as required by programmes such as the FAO Forest Resources Assessment 2000, these reasons are equally applicable.
