Chapter 3 - The Physical Setting

3.5 Sea Floor Charts and Data Sets

Almost all available echo-sounder data have been digitized and plotted to make sea-floor charts. Data have been further processed and edited to produce digital data sets which are widely distributed in CD-ROM format. These data have been supplemented with data from altimetric satellites to produce maps of the sea-floor with horizontal resolution approaching 3 km (Figure 3.14).

1. The British Oceanographic Data Centre publishes the General Bathymetric Chart of the Ocean (GEBCO) Digital Atlas on behalf of the Intergovernmental Oceanographic Commission of UNESCO and the International Hydrographic Organization. The atlas consists primarily of the location of depth contours, coastlines, and tracklines from the GEBCO 5th Edition published at a scale of 1:10 million. The original contours were drawn by hand based on digitized echo-sounder data plotted on base maps.
2. The U.S. National Geophysical Data Center publishes the ETOPO-2 CD-ROM containing values of digital oceanic depths from echo sounders and altimetry and land heights from surveys. Data are interpolated to a 2-minute (2 nautical mile) grid. Ocean data between 64°N and 72°S are from the work of Smith and Sandwell (1997), who combined echo-sounder data with altimeter data from GEOSAT and ERS-1. Seafloor data northward of 64°N are from the International Bathymetric Chart of the Arctic Ocean. Seafloor data southward of 72°S are from the US Naval Hydrographic Office's Digital Bathymetric Data Base Variable Resolution. Land data are from the GLOBE Project that produced a digital elevation model with 0.5 minute (0.5 nautical mile) grid spacing using data from many nations.
3. National governments publish coastal and harbor maps. In the USA, the NOAA National Ocean Service publishes nautical charts useful for navigation of ships in harbors and offshore waters.

Figure 3.14 The sea-floor topography of the ocean with 3km resolution produced from satellite altimeter observations of the shape of the sea surface. From Smith and Sandwell.

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