The Normalized Difference Vegetation Index (NDVI) is computed as follows:

NDVI = (chan 2 - chan 1) / (chan 2 + chan 1)

The NDVI is currently scaled for the values from -0.05 until 0.6. To overcome viewing effects, only passes around noon are shown. NDVI is derived from the data described in the

"NOAA / AVHRR RSGB LEVEL1b Data Set" : http://saturn.unibe.ch/rsbern/noaa/dw/realtime/RSGB_LEVEL1B_DOCU.html

The full path data is made available for the public in JPG format using David Taylor's HRPTReader