BOREAS Regional DEM in Raster Format and AEAC Projection
Summary
This data set is based on the GTOPO30 DEM produced by the USGS EDC. The BOREAS
region (1,000km x 1000km) was extracted from the GTOPO30 data and reprojected by
BOREAS staff into the AEAC projection. The pixel size of these data is 1 km.
The data are stored in binary, image format files.
Note that the binary files of this data set on the BOREAS CD-ROMs have been
compressed using the Gzip program. See section 8.2 for details.
Table of Contents
* 1 Data Set Overview
* 2 Investigator(s)
* 3 Theory of Measurements
* 4 Equipment
* 5 Data Acquisition Methods
* 6 Observations
* 7 Data Description
* 8 Data Organization
* 9 Data Manipulations
* 10 Errors
* 11 Notes
* 12 Application of the Data Set
* 13 Future Modifications and Plans
* 14 Software
* 15 Data Access
* 16 Output Products and Availability
* 17 References
* 18 Glossary of Terms
* 19 List of Acronyms
* 20 Document Information
1. Data Set Overview
1.1 Data Set Identification
BOREAS Regional DEM in Raster Format and AEAC Projection
1.2 Data Set Introduction
This data set is based on the GTOPO30 global Digital Elevation Model (DEM)
produced by the United States Geological Survey (USGS) Earth Resources
Observation System (EROS) Data Center (EDC). The area covering the BOReal
Ecosystem-Atmosphere Study (BOREAS) region (1,000km x 1,000km) was extracted from
the GTOPO30 data and reprojected by BOREAS staff into the BOREAS grid projection.
The pixel size of these data is 1km. The GTOPO30 data set produced by EDC is in
latitude/longitude and has a pixel size of 30 arc seconds. The GTOPO30 data set
is available from the EDC Distributed Active Archive Center (DAAC).
1.3 Objective/Purpose
These data are provided as part of the BOREAS Staff Science GIS Data Collection
Program that included the collection of pertinent map data, in both hard copy and
digital form. The purpose of this data set is to provide users with a data
product that characterizes the topography of the BOREAS Region. This data set is
to be used for modeling purposes at a regional scale.
1.4 Summary of Parameters
Elevation above mean sea level
1.5 Discussion
None.
1.6 Related Data Sets
BOREAS HYD-08 DEM Data over the NSA-MSA and SSA-MSA in the UTM Projection
BOREAS DEM Data over the NSA-MSA and SSA-MSA in the AEAC Projection
GTOPO30 Global 30 Arc Second Elevation Data Set
(available at http://edcwww.cr.usgs.gov/landdaac/gtopo30/gtopo30.html)
(tiles W100N90 and W140N90 of GTOPO30 cover the BOREAS region)
2. Investigator(s)
2.1 Investigator(s) Name and Title
David E. Knapp
BOREAS Information System Staff Member
2.2 Title of Investigation
BOREAS Staff Science GIS Activities
2.3 Contact Information
Contact 1
----------
David E. Knapp
NASA/GSFC
Greenbelt, MD
(301) 286-1424
(301)286-0239 (fax)
David.Knapp@gsfc.nasa.gov
Contact 2
-----------
Kristine Verdin
USGS/EROS Data Center
Sioux Falls, SD
(605) 594-6002
kverdin@dg1.cr.usgs.gov
3. Theory of Measurements
This data product was reprojected from a DEM product by EDC. It is intended to
represent the terrain at a regional scale.
4. Equipment
Users of this data set are referred to the EDC DAAC to obtain background
information on how these data were compiled.
4.1 Sensor/Instrument Description
Unknown.
4.1.1 Collection Environment
Unknown.
4.1.2 Source/Platform
Unknown.
4.1.3 Source/Platform Mission Objectives
Unknown.
4.1.4 Key Variables
Elevation above mean sea level
4.1.5 Principles of Operation
Unknown.
4.1.6 Sensor/Instrument Measurement Geometry
Unknown.
4.1.7 Manufacturer of Sensor/Instrument
Unknown.
4.2 Calibration
Unknown.
4.2.1 Specifications
Unknown.
4.2.1.1 Tolerance
Unknown.
4.2.2 Frequency of Calibration
Unknown.
4.2.3 Other Calibration Information
5. Data Acquisition Methods
The original data were acquired from personnel at the USGS EDC. EDC personnel
used Digital Terrain Elevation Data (DTED) from Canada and resampled it to 30 arc
seconds using a nearest neighbor resampling method. Any areas that were not
covered by DTED were filled in with gridded contour data from the Digital Chart
of the World (DCW). These data were gridded by EDC using the TOPOG software
package. The stream network from the DCW was used for drainage enforcement.
The data covering the BOREAS region were extracted from the EDC DEM by BOREAS
Information System (BORIS) staff and reprojected into the BOREAS grid projection.
6. Observations
6.1 Data Notes
Unknown.
6.2 Field Notes
Unknown.
7. Data Description
7.1 Spatial Characteristics
7.1.1 Spatial Coverage
The area covered by this DEM is a 1,000 km x 1,000 km area that roughly straddles
the Manitoba-Saskatchewan border in Canada.
The outside corners of the corner pixels of the data set are as follows:
The North American Datum 1983 (NAD83) corner coordinates of the BOREAS region
are:
BOREAS
Corner Latitude Longitude X (km) Y (km)
------------------------------------------------------------
Northwest 58.979 N 111.000 W 0.000 1000.000
Northeast 58.844 N 93.502 W 1000.000 1000.000
Southwest 51.000 N 111.000 W 0.000 0.000
Southeast 50.089 N 96.969 W 1000.000 0.000
7.1.2 Spatial Coverage Map
Not available.
7.1.3 Spatial Resolution
These data were gridded to a cell size of 1,000 meters in both the X and Y
directions.
7.1.4 Projection
The area mapped is projected in the BOREAS grid projection, which is based on the
ellipsoidal version of the Albers Equal Area Conic (AEAC) projection. The
projection has the following parameters:
Datum: NAD83
Ellipsoid: GRS80 or WGS84
Origin: 111.000�W 51.000�N degrees
Standard Parallels: 52� 30' 00"N
58� 30' 00"N
Units of Measure: kilometers
7.1.5 Grid Description
7.2 Temporal Characteristics
7.2.1 Temporal Coverage
Not applicable
7.2.2 Temporal Coverage Map
Not available.
7.2.3 Temporal Resolution
The sources of data produced by EDC were from different dates. The temporal
characteristics of these data are insignificant, considering the fact that these
are elevation data at a very coarse scale (a pixel is 1,000m x 1,000m).
7.3 Data Characteristics
7.3.1 Parameter/Variable
Elevation above mean sea level
7.3.2 Variable Description/Definition
Elevation above mean sea level - The vertical distance between a plane at mean
sea level and a parallel plane intersecting the given geographic point.
7.3.3 Unit of Measurement
Meters
7.3.4 Data Source
The original data were acquired from personnel at the USGS EDC.
7.3.5 Data Range
Not available.
7.4 Sample Data Record
Not applicable to binary raster images.
8. Data Organization
8.1 Data Granularity
The smallest amount of data that can be ordered from this data set is the entire
data set covering the entire BOREAS region.
8.2 Data Format(s)
8.2.1 Uncompressed Data Files
The data product contains two files:
File 1: ASCII header file containing 8 records of 80 bytes.
File 2: DEM data file consisting of 1,000 records containing 2,000 bytes each.
Each 2,000-byte record is an image line and contains 1,000 2-byte (16-bit)
integers stored as low-order byte first.
8.2.2 Compressed CD-ROM Files
On the BOREAS CD-ROMs, file 1 is stored as ASCII text; however, file 2 has been
compressed with the Gzip compression program (file name *.gz). These data have
been compressed using gzip version 1.2.4 and the high compression (-9) option
(Copyright (C) 1992-1993 Jean-loup Gailly). Gzip (GNU zip) uses the Lempel-Ziv
algorithm (Welch, 1994) used in the zip and PKZIP programs. The compressed files
may be uncompressed using gzip (-d option) or gunzip. Gzip is available from
many websites (for example, ftp site prep.ai.mit.edu/pub/gnu/gzip-*.*) for a
variety of operating systems in both executable and source code form. Versions
of the decompression software for various systems are included on the CD-ROMs.
9. Data Manipulations
9.1 Formulae
9.1.1 Derivation Techniques and Algorithms
As stated in Section 5, these data were reprojected from latitude/longitude
coordinates to the BOREAS grid projection. The BOREAS grid is based on the
ellipsoidal version of the AEAC projection as defined within the NAD83. The
parameters used for this projection are given in Section 7.1.4. A nearest
neighbor resampling method was used in reprojecting the data.
9.2 Data Processing Sequence
9.2.1 Processing Steps
BORIS staff processed the data by:
1) Extracting the DEM from EDC into ARC/INFO grid.
2) Creating a projection file to define input (latitude/longitude) and output
(AEAC) projections.
3) Reprojecting the original DEM into the AEAC projection using the ARC/INFO
PROJECT command.
4) Writing the reprojected data file to tape.
5) Copy the ASCII and compress the binary files for release on CD-ROM.
9.2.2 Processing Changes
None.
9.3 Calculations
9.3.1 Special Corrections/Adjustments
None.
9.3.2 Calculated Variables
None.
9.4 Graphs and Plots
None.
10. Errors
10.1 Sources of Error
The TOPOG program interpolates the values to grid cells from vector data
(digitized contours). Errors occur where the original vector data are too sparse
spatially, e.g., in flat lowland areas.
10.2 Quality Assessment
No quality assessment is available; therefore, caution is advised to those who
use this product.
10.2.1 Data Validation by Source
Not available.
10.2.2 Confidence Level/Accuracy Judgment
Not available.
10.2.3 Measurement Error for Parameters
Not available.
10.2.4 Additional Quality Assessments
Not available.
10.2.5 Data Verification by Data Center
After extracting and reprojecting the data, BORIS staff displayed and visually
reviewed the data. No anomalies or errors were detected in this review.
11. Notes
11.1 Limitations of the Data
Elevation variations can exist within the lakes, especially large lakes, due to
the reason given in Section 10.1.
11.2 Known Problems with the Data
See Sections 10.1 and 11.1.
11.3 Usage Guidance
It is important for the user to keep in mind that this data set is at a coarse
scale and might not be useful at other scales.
Before uncompressing the Gzip files on CD-ROM, be sure that you have enough disk
space to hold the uncompressed data files. Then use the appropriate
decompression program provided on the CD-ROM for your specific system.
11.4 Other Relevant Information
The original EDC GTOPO30 Global 30 Arc Second Elevation Data Set is available at
http://edcwww.cr.usgs.gov/landdaac/gtopo30/ (map tiles W100N90 and W140N90 of
GTOPO30 cover the BOREAS region).
12. Application of the Data Set
These data could be used by anyone needing elevation data at coarse resolutions
over large areas.
13. Future Modifications and Plans
None.
14. Software
14.1 Software Description
The data manipulation capabilities in the ARC/INFO software package (Version 7.0)
were used to reproject the data. ARC/INFO is a GIS package developed by the
Environmental Systems Research Institute, Inc. (ESRI).
Gzip (GNU zip) uses the Lempel-Ziv algorithm (Welch, 1994) used in the zip and
PKZIP commands.
14.2 Software Access
ARC/INFO is a proprietary software package produced byESRI:
Environmental Systems Research Institute, Inc.
380 New York St.
Redlands, CA 92373-8100
Gzip is available from many websites across the net (for example) ftp site
prep.ai.mit.edu/pub/gnu/gzip-*.*) for a variety of operating systems in both
executable and source code form. Versions of the decompression software for
various systems are included on the CD-ROMs.
15. Data Access
15.1 Contact Information
Ms. Beth Nelson
BOREASData Manager
NASA/GSFC
Greenbelt, MD
(301) 286-4005
(301) 286-0239 (fax)
Elizabeth.Nelson@gsfc.nasa.gov
15.2 Data Center Identification
See Section 15..1
15.3 Procedures for Obtaining Data
Users may place data requests by telephone, electronic mail, or fax.
15.4 Data Center Status/Plans
The regional DEM data are available from the Earth Observing System Data and
Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed
Active Archive Center (DAAC).
The BOREAS contact at ORNL is:
Merilyn Gentry
User Services/Data Coordinator
Oak Ridge National Laboratory DAAC
Oak Ridge, TN
(423) 241-3952
ornldaac@ornl.gov
16. Output Products and Availability
16.1 Tape Products
The DEM data can be made available on 8-mm, Digital Archive Tape (DAT), or 9-
track tapes at 6250 or 1600 Bytes Per Inch (BPI).
16.2 Film Products
None.
16.3 Other Products
These data are available on the BOREAS CD-ROM series.
17. References
17.1 Platform/Sensor/Instrument/Data Processing Documentation
Snyder, J.P. 1987. Map Projections - A Working Manual. USGS Professional Paper
1395.
TOPOG User Guide (Version 5.0). 1994. Division of Water Resources, CSIRO.
Canberra, Australia.
Welch, T.A. 1984, A Technique for High Performance Data Compression, IEEE
Computer, Vol. 17, No. 6, pp. 8 - 19.
17.2 Journal Articles and Study Reports
Sellers, P., F. Hall. 1994. Boreal Ecosystem-Atmosphere Study: Experiment Plan.
Version 1994-3.0, NASA BOREAS Report (EXPLAN 94).
Sellers, P., F. Hall. 1996. Boreal Ecosystem-Atmosphere Study: Experiment Plan.
Version 1996-2.0, NASA BOREAS Report (EXPLAN 96).
Sellers, P., F. Hall, and K.F. Huemmrich. 1996. Boreal Ecosystem-Atmosphere
Study: 1994 Operations. NASA BOREAS Report (OPS DOC 94).
Sellers, P., F. Hall, and K.F. Huemmrich. 1997. Boreal Ecosystem-Atmosphere
Study: 1996 Operations. NASA BOREAS Report (OPS DOC 96).
Sellers, P., F. Hall, H. Margolis, B. Kelly, D. Baldocchi, G. den Hartog, J.
Cihlar, M.G. Ryan, B. Goodison, P. Crill, K.J. Ranson, D. Lettenmaier, and D.E.
Wickland. 1995. The boreal ecosystem-atmosphere study (BOREAS): an overview and
early results from the 1994 field year. Bulletin of the American Meteorological
Society. 76(9):1549-1577.
Sellers, P., F. Hall. 1997. BOREAS Overview Paper. JGR Special Issue (in press).
17.3 Archive/DBMS Usage Documentation
None.
18. Glossary of Terms
None.
19. List of Acronyms
AEAC - Albers Equal Area Conic
BOREAS - BOReal Ecosystem-Atmosphere Study
BORIS - BOREAS Information System
BPI - Bytes Per Inch
DAAC - Distributed Active Archive Center
DCW - Digital Chart of the World
DAT - Digital Archive Tape
DTED - Digital Terrain Elevation Data
DEM - Digital Elevation Model
EDC - EROS Data Center
EOS - Earth Observing System
EOSDIS - EOS Data and Information System
EROS - Earth Resources Observation System
ESRI - Environmental Systems Research Institute, Inc.
GSFC - Goddard Space Flight Center
NAD27 - North American Datum of 1927
NAD83 - North American Datum of 1983
NASA - National Aeronautics and Space Administration
NSA - Northern Study Area
ORNL - Oak Ridge National Laboratory
PANP - Prince Albert National Park
SSA - Southern Study Area
URL - Uniform Resource Locator
USGS - United States Geological Survey
UTM - Universal Transverse Mercator
20. Document Information
20.1 Document Revision Dates
Written: 17-Mar-1995
Last Updated: 30-Jul-1998
20.2 Document Review Dates
BORIS Review: 05-Jun-1997
Science Review:
20.3 Document ID
20.4 Citation
The efforts of the BORIS staff in making this data available are greatly
appreciated.
20.5 Document Curator
20.6 Document URL
Keywords
--------------------
DIGITAL ELEVATION MODEL
DEM
TERRAIN
ELEVATION
Region_AEAC_DEM.doc
08/18/98