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).
- 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
The atlas consists primarily of the location of depth contours, coastlines,
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.
- 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.
- 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.