Rocky Mountain Research Station Publications

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RMRS-GTR-9CD: NDVI and derived image data: Data archives 1997

Burgan, Robert E.; Chase, Carolyn H. 1998. NDVI and derived image data: Data archives 1997. Gen. Tech. Rep. RMRS-GTR-9-CD. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 5 CD-ROM set.

This CD-ROM contains raw raster data in byte format. There are 13,251,843 bytes in each image of the conterminous United States. Full images can be viewed with a standard Geographic Information System, or programs provided on the CD-ROM can be used to extract and view portions of the full image. Refer to the "readme" file for complete instructions.

The Normalized Difference Vegetation Index (NDVI) provides a means to observe vegetation greenness from satellite data. The satellites make observations daily for the entire United States, but such factors as cloudiness, smoke or haze, and poor viewing angle can reduce the quality of the observed data. To compensate for this, several days' NDVI observations are composited for each pixel, with only the highest NDVI value observed during the composite period being saved. From 1989 through 1995, 14 days of daily NDVI images were used to make 2 week composites. This greatly reduces problems caused by cloudiness, but it does not entirely eliminate them. Additionally, such a long composite period creates a delay in observing vegetation curing.

In 1996 the composite period was reduced to 7 days. This improves the usefulness of the images during periods of rapid vegetation curing, but it comes at the expense of additional cloud contamination. Regardless of what the composite period is, care must be taken in interpreting the images.

If an NDVI map, or one of the maps derived from NDVI (Visual Greenness, VG; Relative Greenness, RG; Departure From Average Greenness, DA; and Live Shrub Moisture, MO), appears to be affected by cloudiness, look at the image for one period before and one period after the current image. If an area exhibits suspiciously low vegetation greenness and shows higher greenness in the image before or after the current image, the current image is likely showing cloud or smoke contamination.

You will see white areas in some images. These indicate clouds, snow or other nongreen surfaces. Often a "fringe," sometimes rather large, may be evident around cloudy pixels. Snowy areas viewed under clear conditions generally have a narrow band of surrounding low vegetation greenness.

For additional information on the Forest Service's vegetation and fire danger assessment program using satellite data, or comments about the CD-ROM, contact:

Fire Sciences Laboratory
PO Box 8089
Missoula, MT 59807 USA
Phone: (406) 329-4820
FAX: (406) 32924825

This publication is not available online. The contents were published on a CD and are only available in that format. Please click here to order the CD of this publication.

A duplicate CD-ROM may also be purchased from:

National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Phone: (800) 553-6847

Title: RMRS-GTR-9CD: NDVI and derived image data: Data archives 1998
Electronic Publish Date: August 22, 2008
Last Update:
August 22, 2008

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