The Normalised Difference Vegetation Index (NDVI) data are derived from satellite data. The data provides an overview of the status and dynamics of vegetation across Australia, providing a measure of the amount of live green vegetation. The satellite data comes from the Advanced Very High Resolution Radiometer (AVHRR) instruments on board the National Oceanic and Atmospheric Administration (NOAA) series of satellites that are operated by the US (http://noaasis.noaa.gov/NOAASIS/ml/avhrr.html).