US Geological Survey visual mark 
Open-File Report 99-369, version 1.0

Digital elevation model (DEM) of Cascadia, latitude 39N-53N, longitude 116W-133W


compiled by
Ralph A. Haugerud (1)
 

 

This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards or with the North American Stratigraphic Code. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

The data in this report are not suitable for navigation.
 
 
 

U.S. DEPARTMENT OF THE INTERIOR
U.S. GEOLOGICAL SURVEY

This report is only available on the web

Revision History


(1) USGS@UW, Box 351310, Seattle WA 98195
email: rhaugerud@usgs.gov

Introduction

This report contains a 250-meter digital elevation model (DEM) for Cascadia (latitude 39N - 53N, longitude 116W - 133W), a region that encompasses the Cascade volcanic arc, the Cascadia subduction zone, and the Juan de Fuca Ridge system. The DEM is distributed as file cascdem.tar.gz  (39 MB; 78MB uncompressed).

Cascdem.tar.gz includes the following files:
README.txt this document as ASCII text
cascadia.bil data file, about 77 megabytes in size
cascadia.hdr header file
cascadia.stx
cascadia.blw
cascadia.prj ARC/INFO projection file for Cascadia grid
sources.e00 ARC/INFO export file of map of data sources 

The DEM contains elevation values in integer meters, at regularly-spaced points in a Lambert conformal conic projection with standard parallels at latitudes 41.5N and 50.5N, and a central longitude of 124.5W (the "Cascadia" projection.).

This report is on the World-Wide Web at http://geopubs.wr.usgs.gov/open-file/of99-369. It may also be obtained by anonymous ftp at:

    geopubs.wr.usgs.gov
cd to directory
    pub/open-file/of99-369
File cascdem.tar.gz may also be obtained by sending a 2.3 or 5.0 GB, 8mm Exabyte tape with request and return address to
Cascadia DEM
c/o Database Coordinator
U.S. Geological Survey
345 Middlefield Road, MS 975
Menlo Park, CA 94025
The compressed tar file will be returned on the tape.
 

A 1:2,000,000-scale color shaded-relief map prepared from this DEM, with an interpretation of the physiography of Cascadia, is in press as U.S. Geological Survey map I-2689.

To ease data transfer for the widest possible range of users, the DEM is distributed as a BIL (Band Interleave by Line) file, produced with the ARC GRIDIMAGE command. For grids (the ARC term for a DEM in the form of a regular array of height values), such files are more compact than ARC export (.e00) files and USGS DEM-format files, and are much faster to create and import. They can also be read by many applications other than ARC. cascadia.bil is such a file of binary integers. Elevations are stored in cascadia.bil as unsigned positive 2-byte binary integers, in Motorola byte-order (default for Sun hardware), with an offset of 10000. That is, 203 meters is stored as 10203 meters, and values less than 10000 represent negative elevations. Values of 0 in cascadia.bil represent no data. Values are given by row, west to east, starting at the north edge of the region.

To convert CASCADIA files to an ARC grid

Assemble the cascadia.* files (.bil, .blw, .hdr, prj; .stx is not necessary) in one directory. Make this your workspace.
Arc: imagegrid cascadia casc1
Arc: grid
Grid: casc2 = con(casc1 <> 0, casc1 - 10000)
Grid: &sys cp cascadia.prj casc2/prj.adf
If you DESCRIBE casc2 in ARC, you should get
Description of Grid CASC2

Cell Size = 250.000 Data Type: Integer
Number of Rows = 6435 Number of Values = 8555
Number of Columns = 5951 Attribute Data (bytes) = 8

BOUNDARY STATISTICS

Xmin = -738044.062 Minimum Value = -4853.000
Xmax = 749705.938 Maximum Value = 4378.000
Ymin = 101590.289 Mean = -628.692
Ymax = 1710340.289 Standard Deviation = 2076.818

                          COORDINATE SYSTEM DESCRIPTION
Projection              LAMBERT
Zunits                  UNKNOWN
Units                    METERS             Spheroid             CLARKE1866
Parameters:
1st standard parallel                                   41 30  0.000
2nd standard parallel                                   50 30  0.000
central meridian                                       -124 30  0.00
latitude of projection's origin                         38  0  0.000
false easting (meters)                                       0.00000
false northing (meters)                                      0.00000

To use the SOURCES coverage

Sources.e00 is only accessible with ARC/INFO. Copy sources.e00 to an appropriate directory, start ARC/INFO, make this directory your workspace, and type
Arc: import cover sources sources
to convert the export file into a usable coverage named sources.

Coverage sources was created with the ARC GRIDPOLY command from a 250-m grid. It does not provide a usable shoreline!

How the DEM was compiled

To make the DEM, data from many sources were resampled at a 250-m interval in the Cascadia map projection and composited. The software used for projecting the data (ARC/INFO GRID, version 7.0.3) does not allow for explicit registration of the output grid, and as a result there are lateral shifts of potentially as much as one grid cell (250 meters) between blocks of data. These shifts appear to be insignificant at this resolution. Data sets 14, 15, and 16 (see below) were combined, interpolated, and gridded together to produce a surface that is smooth at the data-set boundaries.

One-cell-wide gaps between data blocks that resulted from lateral shifts were filled with the focal mean of surrounding values. Wider gaps were locally present at some shoreline locations, where marine and terrestrial data were truncated at different shorelines. These were filled with value Z = 0.

Marine and terrestrial data were merged with the naive assumption that they are measured in relation to the same vertical datum. This is not so: marine depths are relative to Mean Lower Low Water, whereas terrestrial elevations were measured from datums which are approximately equivalent to Mean Sea Level. The difference is most acute in the southern end of Puget Sound (Washington State), where the vertical datums differ by about 2 meters.

Artifacts

Lack of data makes most of the floor of the northeastern Pacific Ocean appear smooth. Some of the smoothness is real, reflecting a blanket of sediment that smothers the oceanic-ridge topography beneath it. But most of the smoothness simply reflects insufficient data--compare the areas from sources 14, 15, and 16 with adjacent areas of high-resolution multibeam sonar surveys (sources 2 and 3). Similarly, apparent differences in the physiography of the Washington continental slope, relative to adjoining parts of the slope, at least partly reflect differences in data quality. Additional artifacts result from mismatches between sets of source data. Perhaps the most obvious mismatch is at longitude 132°W, extending south from 52°N, where an abrupt change in apparent depth occurs at a source-data boundary. Abrupt northward termination at 46°N of longitudinal ridges in the Juan de Fuca Slope also reflects juxtaposition of differing data sources.

Sources

(Numbers correspond to polygon-IDs in the sources coverage.)
1) WASH_30M2: Thirty-meter (UTM) 7.5-minute quad-format DEMs, most produced by scanning/vectorizing/gridding 1:24000-scale topographic maps. Obtainable from USGS or WDNR. Some produced by stereoprofiling (poor quality), a few produced via Gestalt Photo-Mapper (semi-automated image correlation procedure, which makes mostly-excellent grids of the tops of the trees.) DEMs were merged into larger blocks, then projected/subsampled, and merged to a state-wide grid. Minor holes between data blocks were filled with the focal mean of surrrounding cells

2) SEABEAM: Multi-beam swath bathymetry. Projected/subsampled from 100-m (UTM) grids (National Geophysical Data Center, 1993)

3) PMELTRIM2: Trimmed version of 250-m (Cascadia projection) grid supplied by Andra Bobbitt, Pacific Marine Environmental Laboratories, Newport, Oregon. Data is composite of SEABEAM data collected on research cruises to the Juan de Fuca spreading center. Same data (as 100-m grid) is available from Lamont-Doherty RIDGE Web server

4) NOS_N, NOS_S: Raw digital hydrographic survey data (National Geophysical Data Center, 1998). Used, with USGS 1:100K DLG shorelines (EDCFTP) to construct triangulated irregular networks in UTM coordinates. TINs were gridded, smoothed, projected/subsampled to Cascadia projection, and merged

5) DMA_3AS: Three-arc-second DEMs (geographic grid) from EDCFTP, merged into larger blocks, projected/subsampled to Cascadia projection, and merged into final block. Single-cell-width holes filled with focal mean of surrounding cells. Trimmed to Z > 0 prior to merging onto marine data. After merging with marine data, holes in low-elevation coastal areas patched with Z = 0

6 DTED_3AS: Three-arc-second DEMs (geographic grid) produced by U.S. Defense Mapping Agency. May be purchased from Geomatics Canada. Merged into larger blocks, projected/subsampled, and merged to single block. Areas of bad data along some 1°x1° block boundaries deleted. Trimmed to Z > 0 prior to merging with other data

7) GOLDFINGER: Incomplete 100-meter grid of Oregon continental shelf and slope, provided by Chris Goldfinger, Oregon State University (personal communication, 1994)

8) GFPATCH: Patches to Goldfinger's 100-m grid, produced by interpolating across gaps with TOPOGRID (ARC/INFO 7.0.3, drainage enforcement off)

9) CA_SHELF, OR_SHELF3, WA_SHELF: 1:100,000-scale digital line graphs (DLGs) of bathymetry (EDCFTP), supplemented with 1:100K-scale shoreline DLGs (also EDCFTP) and gridded with TOPOGRID (ARC/INFO 7.0.3, drainage enforcement off.) Gridded at 30 to 100 meter resolution, in UTM coordinates, then projected/subsampled.

10) CA_SHELF_N: Digitized by Haugerud from U.S. Coast and Geodetic Survey (1969). Projected to Cascadia projection, and then gridded with TOPOGRID (ARC/INFO 7.0.3, drainage enforcement off)

11) PUGETSOUND_J:  Projected/subsampled from 300-meter grid of Puget Sound basin (Myrtle Jones, USGS, Tacoma, WA, personal communication, 1994; Jones derived this grid from published point and contour bathymetry)

12) GSC_1KM: One-km grid supplied by Dave Seeman and Tark Hamilton, Geological Survey of Canada-Victoria (personal communication, 1994). Projected, converted to a TIN, gridded, and smoothed. See http://gdcinfo.agg.nrcan.gc.ca/cat/cateng.html for information on purchase of this data

13) MILBANKEPATCH: Defect in GSC_1KM repaired with data from Canadian Hydrographic Service (1993). Point depths digitized, projected, and gridded with TOPOGRID.

14) Digital 1:1,000,000 contours, 100-m contour interval, of NE Pacific (prepared by Florence Wong, USGS, from data of Grim and others, 1992 and Chase and others, 1992) supplemented in areas with no contour control by point data from 1500-meter grid (RIDGE Web server) and, outside extent of 1500 m RIDGE grid, ETOPO5 (National Geophysical Data Center, 1993)

15) RIDGE 1500-m grid

16) ETOPO5 (National Geophysical Data Center, 1993)

Data from 14, 15, and 16 were projected, masked/merged, and then gridded using ANUDEM version 4.4 (Hutchison, 1989; drainage enforcement off):

17) NOYO_PATCH: Small area at head of Noyo Canyon, at edge of northern California continental shelf. Filled by interpolation from surrounding areas with TOPOGRID (ARC/INFO 7.0.3, drainage enforcement off)

References Cited

Canadian Hydrographic Service, 1993, Milbanke Sound: Map 3728, scale 1:76,557.

Chase, T.E., Wilde, P., Normark, W.R., Evenden, G.I., Miller, C.P., Seekins,
B.A., Young, J.D., Grim, M.S., and Lief, C.J., 1992, Map showing bottom
topography of the Pacific continental margin, Cape Mendocino to Point
Conception: U.S. Geological Survey Map I-2090-C, scale 1:1,000,000.

Grim, M.S., Chase, T.E., Evenden, G.I., Holmes, M.L., Normark, W.R., Wilde,
P., Fox, C.J., Lief, C.J., and Seekins, B.A., 1992, Map showing bottom
topography of the Pacific continental margin, Strait of Juan de Fuca to Cape
Mendocino: U.S. Geological Survey Map I-2091-C, scale 1:1,000,000.

Hutchinson, M.F., 1989, A new method for gridding elevation and stream line
data with automatic removal of pits: Journal of Hydrology, v. 106, p. 211-232.
See also http://cres.anu.edu.au/software/anudem.html

National Geophysical Data Center, 1993, Global Relief Data on CD-ROM: See http://www.ngdc.noaa.gov/mgg/fliers/93mgg01.html

National Geophysical Data Center, 1998, NOS hydrographic survey data, US Coastal Waters: see http://www.ngdc.noaa.gov/mgg/fliers/98mgg03.html

U.S. Coast and Geodetic Survey, 1969, 1:250,000-scale bathymetric chart 1308N-12, Point St. George to Point Delgada, 10-meter contour interval.

Addresses of Data Sources

EDCFTP: anonymous ftp from edcftp.cr.usgs.gov, see directories pub/data/DLG
and pub/data/DEM (ftp://edcftp.cr.usgs.gov/pub/data/DLG/100K, ftp://edcftp.cr.usgs.gov/pub/data/DEM/250)

Geomatics Canada: See http://www.geocan.NRCan.gc.ca/

RIDGE Web Server: See http://imager.ldeo.columbia.edu/ridgembs/ne_pac/html/home.html

USGS: phone 1-800-USA-MAPS, or http://edcwww.cr.usgs.gov/dsprod/prod.html

WDNR: Washington Department of Natural Resources, Olympia, WA 98504, phone
360-902-1000