Mapping and monitoring deforestation areas in Amazon region using semi-automatic classification of Landsat Thematic Mapper images

The INPE´s operational project (PRODES) to estimate annual gross deforestation in Amazon region based on manual analysis of 229 TM images faces several problems during the interpretation process (variable scales of different scenes, closing polygons in the interpretation maps due to complexity of deforestation pattern). Thus, the availability of results in a digital format has been restricted. This authors propose an approach to map and monitor deforested areas in the Amazon using digital analysis of TM/Landsat. This methodology will automate the PRODES manual interpretation tasks and will build a GIS database. This approach was developed and validated using TM image Path 231/067 (1997, 1998, and 1999) over Rondonia. The original TM bands were converted to vegetation, soil, and shade fraction images applying a linear mixing model. The selected fraction image was segmented using a region growing algorithm, classified using a per region clustering algorithm and the results were manually edited to generate the final map. Results showed 10,252 km² of deforestation up to 1997; increments in the deforested area for 1998 and 1999 were 695 and 388 km², respectively. A total of 1,149 km² was burned in 1998 (only 16% in recent clear cut areas). The proposed methodology is feasible and very useful for global studies using fine resolution satellite data such as Landsat TM