Amazon Basin Subset of the 8 km x 8 km Resolution Global Pathfinder Advanced Very High Resolution (AVHRR) Land FTP Data

Summary:

This data set, a subset of that produced as part of the NOAA/NASA Pathfinder AVHRR Land (PAL) program, contains the Northern half of the South American continent in a 10-day composite of Normalized Difference Vegetation Index (NDVI) at 8 km resolution. The data, derived from the Advanced Very High Resolution Radiometers (AVHRR) on the "afternoon" NOAA operational meteorological satellites (NOAA-7, -9, -11), cover the period from 1982 to 1992. The Pathfinder Program produces long-term ata sets processed in a consistent manner for global change research.

1. Data Set Overview

Data Set Identification:
Amazon Basin Subset of the 8 km x 8 km Resolution Global Pathfinder Advanced Very High Resolution (AVHRR) Land FTP Data
Data Set Introduction:
This data set, a subset of that produced as part of the NOAA/NASA Pathfinder AVHRR Land (PAL) program, contains the northern portion of the South American continent in a monthly composite of Normalized Difference Vegetation Index (NDVI) at 8 km resolution. The data, derived from the Advanced Very High Resolution Radiometers (AVHRR) on the "afternoon" NOAA operational meteorological satellites (NOAA-7, -9,-11), cover the period from 1982 to 1992. The Pathfinder Program produces long-term data sets processed in a consistent manner for global change research.
Objective/Purpose:
Not Available
Summary of Parameters:
The Normalized Difference Vegetation Index (NDVI) is derived from the visible and near-infrared channel reflectances (0.58 to 0.68 um and 0.73 to 1.10 um, respectively)
Discussion:
Not Available
Related Data Sets:
Not Available

2. Investigator(s)

Investigator(s) Name and Title:
Mary James; Peter Schlesinger, M.A., Daniel Nepstad, Ph.D., Paul Lefebvre, M.S.
Title of Investigation:
Source Data Title:
Pathfinder AVHRR Land Data
Data Preparation Title:
Land-use in Amazonia and the Cerrado of Brazil: State of Knowledge and GIS Database
Contact Information:
1) Source Data Investigator:
Ms. Mary James
Goddard Global Change Data Center
EOS Distributed Active Archive Center(DAAC)
Code 902.2
NASA Goddard Space Flight Center
Greenbelt, Maryland 20771
Phone: 301-614-5224
Fax: 301-614-5268
Email: daacuso@daac.gsfc.nasa.gov
2) Data Preparation Investigators:
Peter Schlesinger / Dan Nepstad / Paul Lefebvre
The Woods Hole Research Center
PO Box 296, 13 Church Street
Woods Hole, MA 02543
Phone: (508) 540-9900
Fax: (508) 540-9700
Email: pschles@whrc.org

3. Theory of Measurements

Spectral Wavelengths
On the NOAA-7, NOAA-9, and NOAA-11 satellites, the AVHRR sensor measures emitted and reflected radiation in five channels (bands) of the electromagnetic spectrum: a visible (0.58 to 0.68 micrometer) band that is used for daytime cloud and surface mapping; a near-infrared (0.725 to 1.1 micrometer) band used for surface water delineation and vegetation cover mapping; a mid-infrared (3.55 to 3.93 micrometer) band used for sea surface temperature and nighttime cloud mapping; a thermal infrared (10.5 to 11.5 micrometer) band used for surface temperature and day and night cloud mapping; and another thermal infrared (11.5 to 12.5 micrometer) band used for surface temperature mapping (Kidwell 1991).
Vegetation Index
The first AVHRR channel is in a part of the spectrum where chlorophyll causes considerable absorption of incoming radiation, and the second channel is in a spectral region where spongy mesophyll leaf structure leads to considerable reflectance. This contrast between responses of the two bands can be shown by a ratio transform; i.e., dividing one band by the other. Several ratio transforms have been proposed for studying different land surfaces (Tucker, 1979). The Normalized Difference Vegetation Index (NDVI) is one such ratio, which has been shown to be highly correlated with vegetation parameters such as green-leaf biomass and green-leaf area and, hence, is of considerable value for vegetation discrimination (Justice et al. 1985).
NDVI Relationships With Geophysical Variables
A ratio between bands is of considerable use in reducing variations caused by surface topography (Holben and Justice 1981). It compensates for variations in radiance as a function of Sun elevation for different parts of an image. The ratios do not eliminate additive effects caused by atmospheric attenuation, but the basis for the NDVI and vegetation relationship holds generally. The soil background contributes a reflected signal apart from the vegetation, and interacts with the overlying vegetation through multiple scattering of radiant energy. Huete (1988) found the NDVI to be as sensitive to soil darkening (moisture and soil type) as to plant density over partially vegetated areas.

4. Equipment

Sensor/Instrument Description:
Not Available
Collection Environment:
Not Available
Source/Platform:
Not Available
Source/Platform Mission Objectives:
Not Available
Key Variables:
Not Available
Principles of Operation:
Not Available
Sensor/Instrument Measurement Geometry:
Not Available
Manufacturer of Sensor/Instrument:
Not Available
Calibration:
Specifications:
Not Available
Tolerance:
Not Available
Frequency of Calibration:
Not Available
Other Calibration Information:
Not Available

5. Data Acquisition Methods

The source data for these subsets were acquired by Anonymous FTP from the site: daac.gsfc.nasa.gov, in the directory /data/avhrr/global_8km/

6. Observations

Data Notes:
Not Available
Field Notes:
Not Available

7. Data Description

Spatial Characteristics:
Spatial Coverage:
Location
Min X -9047548.000
Max X -3879806.250
Min Y -2224256.500
Max Y 1408162.375
In decimal degrees of Longitude and Latitude
Spatial Coverage Map:
Not Available
Spatial Resolution:
8 km x 8 km
Projection:
Goode Interrupted Homolosine Projection
Grid Description:
646 columns by 454 rows
Temporal Characteristics:
Temporal Coverage:
January 1982 to December 1992
Temporal Coverage Map:
Not Available
Temporal Resolution:
10-day and monthly composites
Data Characteristics:
Parameter/Variable:
The NDVI in this subset are scaled to an 8-bit unsigned byte value in the range of 3 to 253. An offset of 128 must be applied via a gain of 0.008 to derive the original ndvi value within the range of -1 to +1. For example, to solve for the ndvi value of the binned 8-bit value of 100, the following equation is used:
NDVI=((100*0.008) - (128*0.008)) or -0.224.
Variable Description/Definition:
Not Available
Unit of Measurement:
Unitless
Data Source:

The original data were collected by the Advanced Very High Resolution Radiometer (AVHRR) flown on the NOAA-series satellites. The data for this subset were downloaded via WWW from the URL ftp://daac.gsfc.nasa.gov/data/avhrr.

A detailed, comprehensive description of the NOAA series satellites, the AVHRR instrument, and the AVHRR GAC 1B data can be found in the NOAA Polar Orbiter Data User's Guide (Kidwell 1991), which can be obtained from NOAA's National Environmental Satellite Data and Information Service (NESDIS).

Data Range:
0-253
Sample Data Record:
Not Applicable

8. Data Organization

Data Granularity:

A general description of data granularity as it applies to the IMS appears in the EOSDIS Glossary.

Each of the 158 granules of this dataset consists of a single tarred and GNU-gzipped file. Each of the tarred and GNU-gzipped files in this dataset contains a single flat binary raster image file and an ASCII documentation file.

Data Format:

Each of the flat binary raster image files in this dataset consists of 454 rows by 646 columns, comprising 293,284 bytes (8-bit unsigned). There are no headers, trailers, or delimiters.

The structure of the ASCII documentation files is as follows (portions have been copied directly from the IDRISI for Windows v. 2.0 Help System, with the permission of the IDRISI Project, Clark University, Worcester, MA):


ITEM DESCRIPTION
title A descriptive name of the file.
data type The type of numbers stored in the file. Allowable entries are byte, integer and real.
file type The format in which the Image file is stored.
columns The number of columns in the image.
rows The number of rows in the image.
ref. system The name of the geographic referencing system used with the file.
ref. units The unit of measure used in the specified reference system. Allowable entries are m, ft, mi, km, deg and radians.
unit dist The scaling factor between the given coordinates and actual measurements on the ground.
min X The minimum X coordinate (left edge) of the image.
max X The maximum X coordinate (right edge) of the image.
min Y The minimum Y coordinate (bottom edge) of the image.
max Y The maximum Y coordinate (top edge) of the image.
pos'n error A measure of the accuracy of the positions in the image.
resolution The inherent resolution of the image. In most cases, this should correspond to the result of dividing the range of reference coordinates in X by the number of columns in the image.
min value The minimum value in the image.
max value The maximum value in the image.
value units The unit of measure of the values in the image. The term classes is used for all qualitative data sets, and that whenever standard linear units are appropriate, that the same abbreviations that are used for reference units should also be used (m, ft, mi, km, deg, rad).
value error This field records the error in the data values that appear in image cells. For qualitative data, this should be recorded as a proportional error. For quantitative data, the value here should be an RMS error figure.
flag value Any value in the image that is not a data value, but rather has a special meaning. If there is no flag value, this entry should remain blank.
flag def'n Definition of the above flag value. The most common data flags are those used to indicate background cells and missing data cells.
legend cats The number of legend categories present.
lineage Description of the history by which the values were recorded/derived.
completeness The degree to which the values describe the subject matter indicated.
consistency The logical consistency of the file.

There are three fill values in each image: 0 is Missing Data Over Land, 1 is Ocean, 2 is Goode's Interrupted Space. Orientation is North to South.

9. Data Manipulations

Formulae:
Derivation Techniques and Algorithms:
Not Available
Data Processing Sequence:
Processing Steps:
Each of the monthly datafiles in this dataset were subset from the source data using the IDRISI for Windows geographic analysis system (Eastman, 1997) to include only the columns 1371-2016 and rows 908-1361 [where the column/row coordinate of the upper left is (0,0)].
Processing Changes:
Not Applicable
Calculations:
Special Corrections/Adjustments:
Not Available
Calculated Variables:
Not Available
Graphs and Plots:
Not Available

10. Errors

Sources of Error:
Not Available
Quality Assessment:
Data Validation by Source:
Not Available
Confidence Level/Accuracy Judgement:
Not Available
Measurement Error for Parameters:
Not Available
Additional Quality Assessments:
Not Available
Data Verification by Data Center:
Not Available

11. Notes

Limitations of the Data:
Not Available
Known Problems with the Data:
Not Available
Usage Guidance:
Not Available
Any Other Relevant Information about the Study:
Not Available

12. Application of the Data Set

The NDVI has been correlated with such physical measurements as total standing biomass, green leaf-area index (LAI) and per cent vegetation cover, but is probably best described as a relative measure of vegetation vigor and photosynthetic activity. It is most often used among other applications as a tool for monitoring temporal changes in vegetation.

13. Future Modifications and Plans

Not Available

14. Software

Software Description:
Two softwares are required to read the files in this dataset:
the shareware tar program tar.exe
the GNU compression utility gzip.exe
Software Access:
The GNU-gzip program (gzip.exe) and shareware tar program (tar.exe) are available via Anonymous FTP from the following site: wuarchive.wustl.edu, in the directory, /systems/msdos/gnuish, files: gzip124x.zip and gnutar.zip

15. Data Access

Contact Information:
1) Source Data Contact:
EOS Distributed Active Archive Center(DAAC)
Code 902.2
NASA Goddard Space Flight Center
Greenbelt, Maryland 20771
Phone: 301-614-5224
Fax: 301-614-5268
Email: daacuso@daac.gsfc.nasa.gov
2) Data Preparation Contact:
Peter Schlesinger / Dan Nepstad / Paul Lefebvre
Woods Hole Research Center
PO Box 296, 149 Woods Hole Rd.
Woods Hole, MA 02543
Phone: (508)540-9900
Fax: (508)540-9700
Email: pschles@whrc.org
Data Center Identification:
Not Applicable
Procedures for Obtaining Data:
Not Applicable
Data Center Status/Plans:
Not Applicable

16. Output Products and Availability

Not Applicable

17. References

The material for this set of metadata were adapted largely and portions copied directly from the on-line document at World Wide Web address:
http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/FTP_SITE/readmes/pal.html

The production and distribution of this data set are funded by NASA's Mission to Planet Earth program. The data are not copyrighted; however, we request that, when you publish data or results using these data, please acknowledge as follows:

The authors wish to thank the Distributed Active Archive Center (Code 902.2) at the Goddard Space Flight Center, Greenbelt, MD, 20771, for producing the data in their present form and distributing them. The original data products were produced under the NOAA/NASA Pathfinder program, by a processing team headed by Ms. Mary James of the Goddard Global Change Data Center; and the science algorithms were established by the AVHRR Land Science Working Group, chaired by Dr. John Townshend of the University of Maryland. Goddard's contributions to these activities were sponsored by NASA's Mission to Planet Earth program.

The original data set from which this subset is derived is part of the Pathfinder Land data set archived at the Goddard DAAC. It is derived from the PAL 8 km Daily data. The Daily data are derived from the NOAA AVHRR Global Area Coverage (GAC) 1B data, available from NOAA's Satellite Active Archive.

Metadata References:

Brown, O.W., J.W. Brown, and R.H. Evans. 1985. Calibration of Advanced Very High Resolution Radiometer observations. Journal of Geophysical Research, 90:11667- 11677.

Eastman, J.R., 1997. IDRISI for Windows Version 2.0. Clark Labs for Cartographic Technology and Geographic Analysis, Clark University, Worcester, MA

Gordon, H.R., J.W. Brown, and R.H. Evans. 1988. Exact Rayleigh scattering calculations for use with the Nimbus- 7 coastal zone color scanner. Applied Optics, 27:2111-2122.

Holben, B.N., and C.O. Justice. 1981. An examination of spectral band ratioing to reduce the topographic effect on remotely sensed data, International Journal of Remote Sensing, 2:115-133.

Huete, A.R. 1988. A soil adjusted vegetation index (SAVI), Remote Sensing of the Environment, 25:295-309.

Justice, C.O., J.R.G. Townshend, B.N. Holben, and C.J. Tucker. 1985. Analysis of the phenology of global vegetation using meteorological satellite data, International Journal of Remote Sensing, 6:1271-1318.

Kidwell, K. 1991. NOAA Polar Orbiter Data User's Guide. NCDC/SDSD. National Climatic Data Center, Washington, DC.

McPeters, R.D., et al. 1993. Nimbus-7 Total Ozone Mapping Spectrometer (TOMS) Data Products User's Guide. NASA Reference Publication 1323.

NGDC. 1993. 5 Minute Gridded World Elevation. NGDC Data, Announcement DA 93-MGG-01. Boulder.

Rao, C.R.N. 1993a. Nonlinearity corrections for the thermal infrared channels of the Advanced Very High Resolution Radiometer: assessment and recommendations. NOAA Technical Report NESDIS-69. NOAA/NESDIS. Washington, DC.

Rao, C.R.N. 1993b. Degradation of the visible and near-infrared channels of the Advanced Very High Resolution Radiometer on the NOAAP9 spacecraft: assessment and recommendations for corrections. NOAA Technical Report NESDIS- 70. NOAA/NESDIS. Washington, DC.

Staylor, W.F. 1990. Degradation rates of the AVHRR visible channel from the NOAA-6, -7, and -9 spacecraft. Journal of Atmospheric and Oceanic Technology, 7:411-423.

Tucker, C.J. 1979. Red and photographic infrared linear combinations for monitoring vegetation. Remote Sensing of the Environment, 8:127-150.

Weinreb, M.P., G. Hamilton, S. Brown, and R.J. Koczor. 1990. Nonlinearity corrections in calibration of Advanced Very High Resolution Radiometer infrared channels. Journal of Geophysical Research, 95:381-7388.

18. Glossary of Terms

Not Available

19. List of Acronyms

Acronym Definition
ASCII American Standard Code for Information Interchange
AVHRR Advanced Very High Resolution Radiometer
DAAC Distribute Active Archive Center
EOS Earth Observing System
FTP File Transfer Protocol
GAC Global Area Coverage
GNU GNU's not UNIX
NASA National Aeronautics and Space Administration
NDVI Normalized Difference Vegetation Index
NESDIS National Environmental Satellite Data and Information Service
NOAA National Oceanic and Atmospheric Administration
PAL Pathfinder AVHRR Land program
RMS Root Mean Square

20. Document Information

Document Revision Date:
October 26, 2004
Document Review Date:
Not Available
Document ID:
(currently leave this blank)
Citation:
(currently leave this blank)
Document Curator:
Not Available
Document URL:
http://whrc.org/LBA_data/Amaz_8K_AVHRR.htm