NDVI (Normalized difference vegetation index) image of central Arizona-Phoenix from a 2005 Landsat Thematic Mapper image

Normalized difference vegetation index (NDVI) produced from the 2005 Landsat Thematic Mapper (TM) image. NDVI is a means of monitoring density and vigour of green vegetation growth using the spectral reflectivity of solar radiation. It is computed as follows: (NIR-RED) / (NIR+RED), where NIR (Near Infra-Red) is the TM band 4 (0.76-0.9 micrometers) and RED is band 3 (0.78-0.82 micrometers).