Frequently Asked Questions about
ETOPO2v2
- What are the datums (horizontal and vertical references) for ETOPO2v2?
The horizontal datum is WGS-84, the vertical datum is Mean Sea Level.
- How does one cite ETOPO2v2?
U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Geophysical Data Center, 2006. 2-minute Gridded Global Relief Data (ETOPO2v2) http://www.ngdc.noaa.gov/mgg/fliers/06mgg01.html
(more about how to cite NGDC/MGG data and images)
- What is the resolution of ETOPO2v2?
The horizontal grid spacing is 2-minutes of latitude and longitude (1 minute of latitude = 1.853 km at the Equator). The vertical precision is 1 meter.
- What is the projection of ETOPO2v2?
ETOPO2v2 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 odd 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 may be 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 ETOPO2v2?
ETOPO2v2 is a database, not a program. You will need imaging or analysis software to use the data.
Download ETOPO2v2 data
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