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Earth Surface & Interior

Vegetation indices are radiometric measures of photosynthetically active radiation absorbed by chlorophyll in the green leaves of vegetation canopies and are therefore good surrogate measures of the physiologically functioning surface greenness level of a region. In a series of articles during the early 1980s, Compton J. Tucker, demonstrated how the Normalized Difference Vegetation Index (NDVI) generated from NOAA’s Advanced Very High Resolution Radiometer (AVHRR) data can be used to map land cover and monitor vegetation changes and desertification at continental and global scales. A simple search on the Web of Science reveals over 5000 articles containing NDVI either in the title or in the abstract. Compton J. Tucker continued to generate the NDVI time series over the past 30 years, in the framework of the Global Inventory Monitoring and Modeling System (GIMMS) project, carefully assembling it from different AVHRR sensors and accounting for various deleterious effects, such as calibration loss, orbital drift, volcanic eruptions, etc. The latest version of the GIMMS NDVI data set spans the period July 1981 to December 2011 and is termed NDVI3g (third generation GIMMS NDVI from AVHRR sensors).

This project provides added details and tips for data access, which reside on OpenNEX (Amazon Web Services s3) and the NEX platform.

The data can be directly downloaded here ecocast.arc.nasa.gov

Or the data can be accessed on amazon's S3, s3://nasanex/AVHRR/GIMMS/

Please browse the wiki pages for more information on data access, file formats, etc...

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Discussions

  • Tana Qian, 5 months, 2 weeks

    I used ENVI to geocorrect the rotated data(by map->registration->select GCPs as 4 corners lon/lat),but finally the number of samples and lines in the head file became 4321 (not 4320) and 2160. I wonder how to create the correct georeferenced NDVI dataset? and could you share a correct head file after being geocorrected( with map info ,coordinate system string) Thankfully,QIAN Tana

  • Johan Viscarra Hansson, 7 months, 2 weeks

    How open the data in Arcgis?

    Dear people in this forum. I want to make a climate change vulnerability map for secant agriculture and need to access and open the data in Arcgis 10.2.2. I don't have ENVI. Can someone guide me?

    Thankfully, Johan V.H.

  • Junchang Ju, 7 months, 3 weeks

    Using ENVI directly view or process NDVI3g data might not be a good idea since the data is saved as big endian integers. I have to swap the bytes before I do any processing on my little endian computer. The original image looks rotated as it is saved by columns rather than the more common by-row format.

  • Jay Angerer, 8 months, 1 week

    Are the NDVI3g files generic binary files? I have tried to read them into ENVI and ERDAS as such using the information provided in the general data description, but these both result in the image being displayed incorrectly.

  • JENNIFER DUNGAN, 8 months

    The data are "generic binary" in the sense of being headerless, band sequential and binary (16-bit signed integer in this case). When I use the following hdr file for ENVI, the images display correctly except that they are transposed. I can then use the Basic Tools/Rotate/Flip Data option to transpose the images to a "north up "orientation.

    ENVI
    description = {
      AVHRR_GIMMS 8km global NDVI x1000}
    samples = 2160
    lines   = 4320
    bands   = 1
    header offset = 0
    file type = ENVI Standard
    data type = 2
    interleave = bsq
    sensor type = AVHRR
    byte order = 1
    

    Hope this is helpful.

  • JENNIFER DUNGAN, 8 months, 2 weeks

    Sorry, I meant on the left side of the page.

  • JENNIFER DUNGAN, 8 months, 2 weeks

    Pawlok, Take a look at the data description (click on "Wiki" ion the right side of this page). There you will find the answer to your question.

    https://nex.nasa.gov/nex/projects/1349/wiki/general_data_description_and_access/

  • Pawlok Dass, 8 months, 2 weeks

    I have a question regarding the AVHRR NDVI 3g data set: What lat/lon does the 1st data (row 1, col 1) correspond to? In other words, if we consider the data to be a 2 dimensional matrix, which corner does row 1 & col 1 correspond to?

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