Figure 15.2 A burn history map of a fresh marsh area in south Louisiana. The map was generated by combining classified November 1990, March 1991, and July 1991 Thematic Mapper images. The burn history map details those marsh areas that were: 1 unburned between November 1990 and July 1991; 2 burned pre-March image and identifiable on the summer image (pre -Spring burns); 3 burned pre-Spring but non separable from unburned marsh in summer (non-detected burns); and 4 burned post-March image (post-Spring burns).