This disc contains two versions of an experimental Global Vegetation
Index, developed by Kevin Gallo of the Land Sciences Branch, Office of
Research and Applications, National Environmental Satellite, Data, and 
Information Service (NESDIS), National Oceanic and Atmospheric
Administration (NOAA).  This CD-ROM contains two versions of the data:

Directory 1MONTH contains monthly maxima derived from the original
                 biweekly computations authored by Gallo.  These data
                 are reprojected to a 10-minute latitude-longitude
                 projection, compatible with the Global Change Data
                 Base (Global-10).  Further information on this version
                 of the data is included in the hardcopy documentation, 
                 and in the README file in this directory.

Directory 2BIWEEK contains the original biweekly GVIs produced by Gallo.
                  These data are provided as a source for analysis at
                  higher temporal resolution.  As they are in the Mercator 
                  projection, they are not immediately compatible with the 
                  Global Change Data Base.  In addition, they have not
                  received the GCDB's quality control analysis.  Additional
                  information is contained in the hardcopy documentation,
                  and in the README file in this directory.

The Satellite Data Services Division of NOAA/NESDIS' National Climatic
Data Center distributes operational Global Vegetation Indices (GVIs) 
derived from the Advanced Very High Resolution Radiometer of the NOAA 
Polar Orbiting Environmental Satellites.  These data may be obtained from:

National Oceanic and Atmospheric Administration
National Environmental Satellite, Data, and Information Service
National Climatic Data Center
Satellite Data Services Division (E/CC6)
Princeton Executive Square, Suite 100
Washington, DC 20233

Telephone: (301) 763-8400

This particular data set was developed by Kevin Gallo to investigate the
benefits of using pre-launch calibration information to improve the
usefulness of the GVI.  Gallo's documentation is contained in the README2
file in this directory on the CD-ROM.

In addition, the National Geophysical Data Center distributes another
experimental monthly compilation of NOAA's operational GVI data.  Other
versions of GVI are planned.

Why so many versions of a data set?

Simply put, single versions of a data set were traditional twenty years ago,
when entire careers were spent compiling knowledge on a specific topic.  
Such information was occasionally compiled by a committee of experts into
a single map on the topic.  Such maps often involved considerable (sometimes
heated!) discussion on how to represent the subject.  Legend categories were
the result of (often agonizing) compromise that didn't completely satisfy
any member of the authorship committee, but which were generally recognized
as valuable instigators of scientific discussion, analysis, and interpre-
tation.

With digital representations, we can now offer several different attempts
to represent the same subject.  Each representation provides a basis for
discussion, analysis, and learning.

The original NOAA operational GVI, available from NOAA/NCDC/SDSD (see above)
have been widely accessible, and have been used by many scientists for
qualitative and semi-quantitative analysis.  One of the major comments of
the operational GVI is that the lack of calibration of the data degrades
the use of the GVI.  Different AVHRR instruments on different satellites
have different calibration characteristics, and these characteristics change
with time.

The Gallo data set was an investigation into the use of simple pre-launch
calibration information in producing a GVI.  It was also a look at the
characteristics of a biweekly compilation, as opposed to alternate daily, 
weekly, 10-daily, and monthly compilations used by others.

The README.REF file in this directory on the CD-ROM contains several 
references to discussions on the Global Vegetation Index.

We encourage you to compare this experimental GVI with others that may be
available to you, from the Global Change Data Base or from other sources.
We believe that increased investigation of alternative methods of producing
and analyzing the GVI will result in an improved understanding of the value
of such data.  Such study will also lead to increased understanding of
global environmental phenomena, including those of global change.

=========================================

The file MANUAL.ASC is an ASCII version of the hardcopy manual of the 
original version of this data set.  The only material lacking from this
file is a reprint of a paper which describes the overall philosophy and
development methods of the Global Change Data Base, of which this CD-ROM
plus the Global Ecosystems Database CD-ROM are part.  That reprint may
be obtained by acquiring the separately published version of this CD-ROM.

The file MANUAL.PS contains an Adobe Postscript (TM) version of MANUAL.ASC.

Both of these MANUAL.* files contain descriptions of software which
accompanies the original CD-ROMs, but which does not accompany this disc.
As this disc is intended to demonstrate GeoVU, the non-windows DOS-based
software is not provided here.  It may be obtained by acquiring the 
separately published CD-ROM containing these data.

This CD-ROM includes a replacement of some data, which were incorrectly
transcribed on the separately published CD-ROMs.  Under the 1BIWEEK\CELL 
directory, the BW85??.img files (where ?? are even integers between 16
and 52) were incorrect.  The data are corrected on this CD-ROM.  The
BW85??.doc files in the corresponding ADOC subdirectory are also 
corrected.

The GVI.MEN file is a menu used by the browse and visualization software
that accompanies this CD-ROM.