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 1,000^m^ x 1,000^m^).

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

BOREAS Data 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 37830-6407

\(865\) 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