NOAA/NOS EEZ Bathymetry

Description

The US Exclusive Economic Zone (EEZ) is a zone that surrounds all US possessions and trust territories to a distance of 200 nautical miles from the coastline. Sovereign rights to all natural resources in this zone were unilaterally declared by Presidential Order on March 10, 1983. The combined area of this zone is equal to two-thirds of all US lands prior to the declaration.

Gridded bathymetric data for the EEZ was released by the National Ocean Service (NOS) of NOAA in 1991. The source data was collected using multibeam swath sounding techniques. The gridded data is available in two forms: a UTM (Universal Transverse Mercator) grid and a Geographic grid. See the table below for details. Data values are negative integers that represent depths in meters. A value of 0 indicates no data.

Grid Information

Coord. System: Geographic (decimal degrees), fixed-angle, or
UTM (meters), fixed-length
Cell Size: Geographic: 15 arcseconds (1/240 of a degree), or
UTM: 250 meters
Tile Dimensions: Geographic: 241 columns and 121 rows (grid/node-registered) or
UTM: lat-dependent number of columns, about 230 rows
Tile Span: Most: 1 degree longitude x 1/2 degree latitude, 1 tile
Alaska: 1.5 degrees longitude x 1/2 degree latitude
Data Type: 2-byte integer
Horizontal Datum: North American Datum 1983 (NAD83), GRS 1980 ellipsoid
Vertical Datum: mean sea level
Vertical Units: meters (negative, below sea-level)
Nodata Value: 0
Formats: Paired ASCII text files (GRD/PRG or DAT/PRU).
Geographic grid data is stored in a file with extension ".GRD", with its geocoding information in a companion file with extension ".PRG". UTM grid data is stored in a file with extension ".DAT", with its geocoding information in a companion file with extension ".PRU".

How to Import

Choose Import DEM → NOAA/NOS EEZ Bathymetry from the File menu and then select the file, which should have a filename extension of "*.grd" (Geographic) or ".dat" (UTM). Before using tools in the Extract menu, go to the Planet Info panel of the File → Set Preferences dialog and set the Earth ellipsoid to either "GRS 1980" or "WGS 1984" (these are almost identical). Otherwise calculations of lengths, areas, slopes, etc. will be less accurate.

Data Source

Word Data Center for Marine Geology and Geophysics (WDC MGG) of the National Geophysical Data Center (NGDC) of the National Oceanic and Atmospheric Administration (NOAA)

Data Availability

This data can be purchased online and is available on various media. It is included on NGDC's Global Relief CD-ROM. It is unclear whether complete coverage of the EEZ is available.

Web Site

Main Page: http://www.ngdc.noaa.gov/mgg/fliers/03mgg03.html

Other Products: http://www.ngdc.noaa.gov/mgg/bathymetry/multibeam/multibeam_products.html

Notes

The US Geological Survey has been charged with surveying this region, and in 1984 launched a project called EEZ-SCAN to study it with a long-range sidescan sonar system called GLORIA (Geological Long-Range Inclined Asdic). For more information on this project see: http://walrus.wr.usgs.gov/gloria.

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