A comparative evaluation of NOAA/AVHRR vegetation indexes for burned surface detection and mapping

The only vegetation index (VI) used in all Advanced Very High Resolution Ra diometer (AVHRR)-based burned area studies performed so far is the normaliz ed difference vegetation index (NDVI), in spite of serious known deficienci es caused by sensitivity to atmospheric conditions and soil background. In this study, the ability of various VI to discriminate between burned and un burned surfaces is compared, using burn maps derived from classification of Landsat thematic mapper (TM) imagery as reference data. After assessing th e discriminatory potential of the AVHRR channels 1-3, the following indexes were compared: the NDVI, the VI 3 (VI3), the global environmental monitori ng index (GEMI), and a modified version of GEMI, call ed GEMI3. VI performa nce was assessed in two ways: with a signal-to-noise ratio measure and a me asure of the commission error resulting from segmentation of the burned are a histograms at a fixed level of omission error, Maps of commission errors were generated for each VI and cross tabulated with a land cover map to ide ntify the land cover types more prone to confusion with burns. The newly pr oposed index GEMI3 performs best, followed by the GEMI, VI3, and finally ND VI, the latter being clearly out performed, even by channel 2 used individu ally.