BOREAS DEM Data over the NSA-MSA and SSA-MSA in the AEAC Projection Summary These data were derived from the original DEMs produced by the BOREAS HYD-08 team. The original DEMs were in the UTM projection, while this product is projected in the AEAC projection (see Section 7 for further projection details). The pixel size of the data is 100 meters, which is appropriate for the 1:50,000- scale contours from which the DEMs were made. The original data were compiled from information available in the 1970s and 1980s. This data set covers the two MSAs that are contained within the SSA and the NSA. 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 DEM Data over the NSA-MSA and SSA-MSA in the AEAC Projection 1.2 Data Set Introduction These Digital Elevation Models (DEMs) were resampled into the BOReal Ecosystem- Atmosphere Study (BOREAS) grid projection from the original DEMs produced by the BOREAS HYD-08 (Hydrology) team. The original DEMs were in the Universal Transverse Mercator (UTM) projection. The pixel size of the data is 100 meters, which is appropriate for the 1:50,000-scale contours from which these DEMs were made. 1.3 Objective/Purpose These data are provided as part of the BOREAS Staff Science Geographic Information System (GIS) Data Collection Program which included the collection of pertinent map data in both hardcopy and digital form. This data set has been processed to provide raster files that can be used for modeling or for comparison purposes. The objective of these DEMs is to provide the BOREAS investigators with a data product that characterizes the topography of the Modeling Sub-Areas (MSAs) in the Albers Equal-Area Conic (AEAC) projection. The original DEMs were produced by HYD-8 in the UTM projection. 1.4 Summary of Parameters Elevation above mean sea level 1.5 Discussion These DEMs were resampled into the AEAC projection from the original DEMs produced by HYD-08. The original DEMs were in the UTM projection. The pixel size of the data is 100 meters, which is appropriate for the 1:50,000-scale contours from which the DEMs were made. 1.6 Related Data Sets BOREAS Regional DEM in Raster Format and AEAC Projection BOREAS HYD-08 DEM Data over the NSA-MSA and SSA-MSA in the UTM Projection 2. Investigator(s) 2.1 Investigator(s) Name and Title Dr. L.E. Band. 2.2 Title of Investigation Simulation of Boreal Ecosystem Carbon and Water Budgets: Scaling from Local to Regional Extents 2.3 Contact Information Contact 1 ----------- David Knapp NASA/GSFC Greenbelt, MD (301) 286-1424 (301) 286-0239 (fax) David.Knapp@gsfc.nasa.gov Contact 2 ----------- Xuewen Wang Dept. Geography, U. Toronto Toronto, Ontario Canada (416) 978-5070 wangx@esker.geog.utoronto.ca Contact 3 ----------- L.E. Band Dept. Geography, U. Toronto Toronto, Ontario Canada (416) 978-3375 lband@eos.geog.utoronto.ca 3. Theory of Measurements This data set was produced for modeling purposes. The DEMs can be used to determine the elevation of a given location and the drainage patterns in the MSAs which are important for understanding the vegetative cover and hydrology of these areas. 4.1 Sensor/Instrument Description The equipment and other data-gathering methods used for compiling the original data are 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 Unknown. 5. Data Acquisition Methods The original data were acquired from the National Topographical Data Base and received by the HYD-08 team from the Canadian Centre for Remote Sensing (CCRS). The data came in Standard Interchange Format (SIF), digitized from 1:50,000 topographic maps. HYD-08 used these contours in the TOPOG software package to create gridded DEMs. BOREAS staff science received the DEMs from HYD-08 in the UTM projection and reprojected them in the Albers Equal Area Conic (AEAC) projection. 6. Observations Not applicable. 6.1 Data Notes None. 6.2 Field Notes Not applicable. 7. Data Description 7.1 Spatial Characteristics 7.1.1 Spatial Coverage Northern Study area (NSA): The area covered by the data is approximately 54 km x 37 km. This area includes areas north-west of Thompson and south of Nelson House, Manitoba. The corner coordinates of the data set are: Longitude Latitude BOREAS X BOREAS Y --------- -------- -------- -------- Northwest 98.92610W 56.13748N 745.900 636.900 Northeast 97.97973W 56.04133N 805.700 636.900 Southwest 99.05263W 55.73102N 745.900 590.900 Southeast 98.11573W 55.63586N 805.700 590.900 Southern Study Area (SSA): The image area that was modeled covers an area that is approximately 54 km x 44 km. This area includes areas just north and east of Candle Lake, Saskatchewan. The corners of the data set are as follows: Longitude Latitude BOREAS X BOREAS Y --------- -------- -------- -------- Northwest 105.22872W 54.13540N 376.400 364.500 Northeast 104.35586W 54.08517N 433.700 364.500 Southwest 105.29095W 53.69173N 376.400 314.900 Southeast 104.42667W 53.64642N 433.700 314.900 7.1.2 Spatial Coverage Map See Section 7.1.1. 7.1.3 Spatial Resolution These data were gridded to a cell size of 100 meters in both the X and Y directions. 7.1.4 Projection The area mapped is projected in the ellipsoidal version of the Albers Equal-Area Conic (AEAC) projection. The projection has the following parameters: North American Datum 1983 Datum: (NAD83) Ellipsoid: GRS80 or WGS84 Origin: 111.000 °W 51.000 °N Standard Parallels: 52° 30' 00"N 58° 30' 00"N Units of Measure:km 7.1.5 Grid Description See Section 7.1.3. 7.2 Temporal Characteristics 7.2.1 Temporal Coverage Most of the maps from which these contours were digitized were made in the 1970s or 1980s. 7.2.2 Temporal Coverage Map Not available. 7.2.3 Temporal Resolution These elevations represent the state of the terrain at a point in time. Most of the elevation data from which the DEMs were produced were collected in the 1970s or 1980s. 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 this point. 7.3.3 Unit of Measurement Meters 7.3.4 Data Source The HYD-08 team received the original data from the CCRS who acquired it from the National Topographical Data Base. 7.3.5 Data Range Not available at this revision. 7.4 Sample Data Record Not applicable to image data. 8. Data Organization 8.1 Data Granularity The smallest amount of data that can be obtained from this data set is the entire data set. 8.2 Data Format(s) 8.2.1 Uncompressed Data Files The data set on tape consists of three files with the following descriptions: File 1: ASCII Header File listing the files that are on the tape. The file contains 9 records of 80 bytes each. File 2: DEM data file for the NSA. This is a binary file containing 1,196 bytes in each of 460 records. Each binary record is a line of the image file and contains 598 2-byte (16-bit) values stored as low-order byte first. Each binary value is the mean elevation above sea level of the location in meters. File 3: DEM data file for the SSA. This is a binary file containing 1,146 bytes in each of 496 records. Each binary record is a line of the image file and contains 573 2-byte (16-bit) values stored as low-order byte first. Each binary value is the mean elevation above sea level of the location in meters. 8.2.2 Compressed CD-ROM Files On the BOREAS CD-ROMs, file 1 listed above is stored as ASCII text; however, files 2 and 3 have 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 These data were reprojected from UTM coordinates to the AEAC projection as defined within NAD83. The origin of the grid is at 111°W, 51°N with standard parallels set to 52.5°N and 58.5°N as prescribed in "Map Projections - A Working Manual," USGS Professional Paper 1395, John P. Snyder, 1987. 9.1 Formulae 9.1.1 Derivation Techniques and Algorithms The original UTM data were placed in the AEAC projection using the nearest- neighbor resampling method. 9.2 Data Processing Sequence 9.2.1 Processing Steps BOREAS Information System (BORIS) personnel processed the data by: 1) Converting the corners of the original DEM to BOREAS grid coordinates 2) Using the four corners of the image as ground control points 3) Resampling the DEM into the BOREAS grid coordinate using a first order polynomial and nearest-neighbor resampling. 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 Please see the documentation for the original DEM for information regarding error. 10.2 Quality Assessment Please see the documentation for the original DEM for information regarding quality assessment. 10.2.1 Data Validation by Source None. 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 applicable. 10.2.5 Data Verification by Data Center BORIS staff visually reviewed the images to see that they did appear to represent a DEM data layer without any obvious anomalies. The only quantitative assessment made was to see that the minimum and maximum elevation values in the raster files approximated those shown on topographic maps of the area. 11. Notes 11.1 Limitations of the Data There are elevation variations within the lakes, especially large lakes because there are no contours in the lakes which can cause a stair step effect in the lakes. Because these DEMs were reprojected from the original DEMs, there may be minor differences in the relationship between neighboring pixels that can result in significant differences if the DEM is used to determine drainage patterns. If your application of these DEMs is sensitive to this problem, it is suggested that the original DEMs (in the UTM projection) be used. 11.2 Known Problems with the Data See Section 11.1. 11.3 Usage Guidance 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 None. 12. Application of the Data Set See Section 11.1. 13. Future Modifications and Plans None. 14. Software 14.1 Software Description The data manipulation capabilities in the EASI/PACE software package (Version 5.2) were used to reproject/grid the data. However, almost any image processing package could have been used to resample this imagery. Gzip (GNU zip) uses the Lempel-Ziv algorithm (Welch, 1994) used in the zip and PKZIP commands. 14.2 Software Access EASI/PACE is a proprietary software package developed by PCI, Inc. Contact PCI for details. PCI, Inc. 50 West Wilmot St. Richmond Hill Ontario, Canada L4B 1M5 (905) 764-0614 (905) 764-9604 (fax) 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 NSA and SSA 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: ORNL DAAC User Services Oak Ridge National Laboratory (865) 241-3952 ornldaac@ornl.gov ornl@eos.nasa.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 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 ASCII - American Standard Code for Information Interchange BOREAS - Boreal Ecosystem-Atmosphere Study BORIS - BOREAS Information System BPI - Bytes Per Inch CD-ROM - Compact Disk-Read-Only-Memory DAAC - Distributed Active Archive Center DAT - Digital Archive Tape DEM - Digital Elevation Model EOS - Earth Observing System EOSDIS - EOS Data and Information System GMT - Greenwich Mean Time GSFC - Goddard Space Flight Center MSA - Modeling Sub-Area NAD27 - North American Datum 1927 NAD83 - North American Datum 1983 NASA - National Aeronautics and Space Administration NSA - Northern Study Area ORNL - Oak Ridge National Laboratory PANP - Prince Albert National Park SIF - Standard Interchange Format SSA - Southern Study Area URL - Uniform Resource Locator UTM - Universal Transverse Mercator WWW - World Wide Web 20. Document Information 20.1 Document Revision Dates Written: 15-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 NSA and SSA DEM product was processed by BORIS from the original data supplied by Dr. Larry Band. The contribution of Dr. Band and BORIS in completing this data set are greatly appreciated. 20.5 Document Curator 20.6 Document URL Keywords -------------------- DIGITAL TERRAIN DEM TERRAIN ELEVATION NSA_SSA_DEM.doc 08/18/98