Identification_Information:
  Citation:
    Citation_Information:
      Originator: U.S. Department of Commerce, National Oceanic and Atmospheric Administration (NOAA), National Geophysical Data Center (NGDC)
      Publication_Date: 2001
      Title: Pacific Coast Subset of ETOPO2 Global 2-Minute Gridded Elevation Data
      Geospatial_Data_Presentation_Form: raster digital data
      Online_Linkage: \\Molib01\GIS_Library\Elevation\Land_and_Water\DEMs\ETOPO2\etopo2_pc
  Description:
    Abstract: Pacific Coast Subset of ETOPO2 2-Minute Gridded Global Elevations from NOAA/NGDC.  The vertical (z-values) are in meters.
    Purpose: Assess elevations (terrestrial and bathymetric).
    Supplemental_Information:
      -- BEGIN EXCERPTS FROM ORIGINAL DOCUMENTATION - THIS INFORMATION MAY NOT BE CURRENT --

      The following are excerpts from: 
      http://www.ngdc.noaa.gov/mgg/global/relief/ETOPO2/readme.txt
      http://www.ngdc.noaa.gov/mgg/fliers/01mgg04.html
      as accessed in 2006.07.

      --

      ETOPO2 Global 2-Minute Gridded Elevation Data

      Data: Land Elevations and Ocean Bathymetry

      Raw 2-minute grids in:

      1.  big-endian (ETOPO2.raw.bin) & 
      2.  little-endian (ETOPO2.dos.bin)

      formats (16-bit signed integers, 10800 columns x 5400 rows)

      For full information about ETOPO2, including searching, extraction,
      display capabilities, please see

      http://www.ngdc.noaa.gov/mgg/fliers/01mgg04.html

      The full GEODAS custom grid functionality is now online:
      You can now produce and download custom grids from ETOPO2 on-line
      for free: 

      http://www.ngdc.noaa.gov/mgg/gdas/gd_designagrid.html
      
      warning: you do not need to download the full database, just run
      designagrid on-line.


      Frequently Asked Questions:

      * What are the datums (horizontal and vertical references) for ETOPO2?

      The horizontal datum is WGS-84, the vertical datum is Mean Sea Level.

      * How does one cite ETOPO2?

      U.S. Department of Commerce, National Oceanic and Atmospheric
      Administration, National Geophysical Data Center, 2001. 2-minute Gridded
      Global Relief Data (ETOPO2) 
      http://www.ngdc.noaa.gov/mgg/fliers/01mgg04.html

      * What is the resolution of ETOPO2?

      The horizontal resolution is 2-minutes of latitude and longitude (1.853
      km at the Equator). The vertical resolution is 1 meter.

      * What is the projection of ETOPO2?

      ETOPO2 is in the Cylindrical Equidistant Projection (sometimes called
      Latitude-Longitude, or Geographic).

      * What do the grid data actually represent?

      The grid values represent the elevation at the grid intersections at
      even multiples of 2 minutes of latitude and longitude, averaged over the
      cell's area.

      * Is the sea floor really that bumpy, and what are the long, straight
      lines on the ocean floor that converge on places like San Diego and
      Bermuda?

      The "orange-peel" look of the sea floor is mostly an artifact of the
      satellite altimetry technology and its interpretation of ocean surface waves.
      The straight lines are where direct shipborne measurements have been included
      in the data as "ground truth". These measurements help calibrate, but do not
      correspond 100 percent to the radar altimetry. See W.H.F. Smith and D.T.
      Sandwell, 1997, Global Sea Floor Topography from Satellite Altimetry and Ship
      Depth Soundings, Science 277 (5334), p.1956-1962.

      * What about shallow (<200m) water?

      The satellite altimetry works best in deep water and can distinguish
      many undersea features that are not otherwise surveyed directly. In shallow
      water, the gravitational effects that can be measured from the satellite are
      too small to be reliable. In US waters and some other areas, local
      high-resolution survey data have been used where available.

      * How do I run ETOPO2?

      ETOPO2 is a database, not a program. You will need imaging or analysis
      software to use the data.


      Technical contact:

      Dr. Peter W. Sloss
      (303) 497-6119
      peter.w.sloss@noaa.gov


      revised Wed Jul 13 2005 13:05:23 GMT-0600 (Mountain Daylight Time) W3C

      --

      A newly constructed global elevation data base gridded at 2-minute (latitude-longitude) resolution 
      *both little-endian (Intel, PC, VAX) and big-endian (Sun, Macintosh) data bases for the entire globe 
      *see "Gridded Data Formats" below)

      The seafloor data between latitudes 64° North and 72° South are from the work of Smith and Sandwell (1997). These data were derived from satellite altimetry observations combined with carefully, quality-assured shipboard echo-sounding measurements, by Dr. Walter H.F. Smith, of the NOAA Laboratory for Satellite Altimetry and Dr. David T. Sandwell, of the Institute of Geophysics and Planetary Physics at the University of California, San Diego. Data version 8.2 is used here. 
      For reference on generation of these data, consult: 
      W.H.F. Smith and D.T. Sandwell, 1997, Global Sea Floor Topography from Satellite Altimetry and Ship Depth Soundings, Science 277 (5334), p.1956-1962. 

      Seafloor data southward of 72° South are from the US Naval Oceanographic Office's (NAVOCEANO) Digital Bathymetric Data Base Variable Resolution (DBDBV), version 4.1, gridded at 5 minute spacing; some data in this region are from the older DBDB5 (these data were also used in ETOPO5). Seafloor data northward from 64° North are from the new International Bathymetric Chart of the Arctic Ocean (IBCAO) Version 1. 
      For reference on generation of the IBCAO data, consult: 
      Jakobsson,M., N.Z. Cherkis, J. Woodward, R.Macnab, and B. Coakley. New grid of Arctic bathymetry aids scientists and mapmakers; Eos,Transactions, American Geophysical Union, v.81, no.9, p. 89,93,96. 

      Land topography is from the GLOBE Project, an internationally designed, developed, and independently peer-reviewed global digital elevation model (DEM), at a latitude-longitude grid spacing of 30 arc-seconds (30"). The GLOBE Task Team was established by the Committee on Earth Observation Satellites (CEOS). It is part of Focus I of the International Geosphere-Biosphere Programme - Data and Information System. Primary contributors to the GLOBE database are: (Click here for more details.) 
      National Imagery and Mapping Agency (formerly Defense Mapping Agency), Fairfax, Virginia, USA 
      Geographical Survey Institute, Tsukuba, Japan 
      Australian Surveying and Land Information Group, Canberra, ACT, Australia 
      Jet Propulsion Laboratory, Pasadena, California, USA 
      University College London, UK 
      DLR-German Remote Sensing Data Center, Oberpfaffenhofen, Germany 
      NOAA National Geophysical Data Center, Boulder, Colorado, USA 
      USGS EROS Data Center, Sioux Falls, South Dakota, USA 

      Data Base Assembly

      The five major data sources were assembled into the single ETOPO2 2-minute data base without formal edge matching or other methods that alter the data as initially posted. Higher-resolution data take precedence: data derived from GLOBE mask all other data, Smith/Sandwell data come next, followed by IBCAO, with the 5-minute data filling any gaps. Data values >= 0 are assumed to be land (there are, of course, a few areas with land below sea level that will also therefore look like ocean data, but their values have not been flagged or altered artificially). 

      Five-minute data from DBDBV and ETOPO5 and 30-second data from GLOBE were regridded to 2 minute spacing by bicubic spline interpolation. IBCAO data were originally gridded in a polar stereographic projection; these data were interpolated along lines of constant latitude at 2 minute steps for every 2 minutes of latitude from 72° North to the pole. 

      Gridded Data Formats

      There are two copies of the complete ETOPO2 data base in 16-bit signed integer format in the "RAWGRIDS" directory on the CD-ROM. "ETOPO2.raw" is a big-endian (Sun, Macintosh) version; "ETOPO2.dos" is in little-endian format for Intel (PC) and DEC (Vax) computers. The data are cell-centered, with an array size of 10800 columns x 5400 rows; coverage is from 180° West to 179° 58' East and 90° North to 89° 58' South. A data record for the South Pole is not in these files -- assume 2810m as the elevation. 

      ETOPO2 Sources
      
      Data Sources:
      Smith/Sandwell
      The "Smith/Sandwell" data base is a worldwide set of 2-minute gridded ocean bathymetry derived from 1978 satellite radar altimetry of the sea surface that was interpreted as gravity anomalies and extrapolated to depth equivalents. The version contained in ETOPO2 is 8.2. For a detailed technical discussion of the methodology, click here for more details. 

      GLOBE
      The "Global Land One-kilometer Base Elevation" (GLOBE) data base is made up of data sets from more than eight US and foreign agencies. It covers all of the world's land masses at a resolution of 0.5 minute of latitude and longitude, which is approximately one kilometer at the equator. Click here for more details. 

      DBDBV
      The "Digital Bathymetric Data Base, Variable-resolution" (DBDBV) is a digital bathymetric data base that provides ocean depths at various gridded resolutions. DBDB-V was developed by NAVOCEANO (Naval Oceanographic Office) to support the generation of bathymetric chart products, and to provide bathymetric data to be integrated with other geophysical and environmental parameters for ocean modeling. The version contained in ETOPO2 is 4.1. 

      IBCAO
      The goal of the International Bathymetric Chart of the Arctic Ocean (IBCAO) initiative is to develop a digital data base that contains all available bathymetric data north of 64 degrees North, for use by mapmakers, researchers, and others whose work requires a detailed and acurate knowledge of the depth and the shape of the Arctic seabed. the version contained in ETOPO2 is 1.0. Click here for more details. 

      DBDB5
      The "Digital Bathymetric Data Base 5 minute" (DBDB5) was assembled by the US Naval Oceanographic Office in the early 1980's from computer interpolation of existing contour maps of ocean basins. It is included in ETOPO2 to fill in a few areas in the Antarctic that are too for south to be covered by the satellite-based bathymetry. Along with several land data bases, DBDB5 was incorporated into a full worldwide 5 minute elevation grid, called ETOPO5. Click here for more details. 

      --

      -- END EXCERPTS FROM ORIGINAL DOCUMENTATION --
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      Theme_Keyword: geoscientificInformation
      Theme_Keyword: oceans
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Data_Quality_Information:
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    Process_Step:
      Process_Description: Downloaded from http://www.ngdc.noaa.gov/mgg/global/relief/ETOPO2/ and converted from floating point to integer in ESRI grid format.  Clipped to a regional area (approximately parts of Canada, USA, Mexico) and converted to California Teale Albers NAD83.
      Process_Date: 20060701
      Process_Contact:
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            Contact_Person: Will Patterson
            Contact_Organization: California Department of Fish and Game
          Contact_Electronic_Mail_Address: geodata@dfg.ca.gov
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    Row_Count: 1510
    Column_Count: 1677
    Vertical_Count: 1
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        Contact_Organization: California Department of Fish and Game
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