10 Day NDVI Composite Data from the Global Land 1-KM AVHRR Project (1992-1996)

The global land 1-km data set project represents an international effort to acquire, archive, process, and distribute 1-km AVHRR data of the entire global land surface in order to meet the needs of the international science community. A network of 29 high resolution picture transmission (HRPT) stations, along with data recorded by the National Oceanic and Atmospheric Administration (NOAA), has been acquiring daily global land coverage since 1 April, 1992. A data set of over 40,000 AVHRR images has been archived and made available for distribution by the United States Geological Survey, EROS Data Center (EDC) and the European Space Agency (ESRIN).

Under the guidance of the International Geosphere Biosphere Programme, processing standards for the AVHRR data have been developed for calibration, atmospheric correction, geometric registration, and the production of global 10-day maximum normalized difference vegetation index (NDVI) composites. The major uses of the composites are related to the study of surface vegetation cover.

The NDVI is the difference of near-infrared (NIR, channel 2) and visible (VIS, channel 1) reflectance values normalized over the sum of channels 1 and 2 [(NIR-VIS)/(NIR+VIS)]. The NDVI equation produces values in the range of -1.0 to 1.0, where increasing positive values indicate increasing green vegetation and negative values indicate nonvegetated surface features such as water, barren, ice, and snow or clouds.

The data are available for April 1992 - September 1993 and February 1995 - May 1996.

The original data resolution is 1km but the web interface at the EDC DAAC allows for the download of subsampled data at 2, 4, 8, and 16 km resolutions. The web interface also allows for both global data and geographical subsets of the global data. Composited in 10-day increments, each 10-day record includes the following bands or channels:

1 AVHRR channel 1
2 AVHRR channel 2
3 AVHRR channel 3
4 AVHRR channel 4
5 AVHRR channel 5
6 NDVI
7 Satellite zenith
8 Solar zenith
9 Relative azimuth
10 Date Index

In addition to the composited data, stitched half-orbital data in NOAA's raw, level 1b format are also available for downloading. If obtaining the data over the Internet is not feasible, global data can be requested on 8 mm magnetic tapes. Contact the EDC DAAC for further information.