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ETOPO2 Global 2 Minute Elevations
Source: NOAA National Geophysical Data Center
Created October 2001 - New Features:
-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 GEODAS data access system, which allows searching, extraction, display, and reformatting of the data
-Color shaded relief images derived from the data displayed as 64, 512, and 1350-pixel squares representing 45° square areas
Major Sources of Data:
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.
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.
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:
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.
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.
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.
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.
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.
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.
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.