ETOPO1 Data Sources
ETOPO1 was built in two versions: an "Ice Surface" version that depicts the surface of the Antarctic and Greenland ice sheets, and a "Bedrock" version that depicts the bedrock underneath the two ice sheets. Most data sources were used in developing both versions, the exception being the RAMP topography of the surface of the Antarctic Ice Sheet, and the bedrock DEMs for each ice sheet. All data sets were converted to WGS84 geographic coordinates before building ETOPO1. The Caspian Sea data were shifted vertically to mean sea level to be consistent with the other data sets.
ETOPO1 Ice Surface Data Sources
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ETOPO1 Bedrock Data Sources
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- GLOBE Topography
The Global Land One-kilometer Base Elevation data set is a thoroughly designed, documented and reviewed 30 arc-second (~1 km) topographic relief model of Earth that was created by NGDC (now NCEI). It was created by combining topographic data sets from U.S. and foreign agencies. ETOPO1 incorporates GLOBE topographic data in regions outside the SRTM data coverage area, principally north of 60° N.
- Measured and Estimated Seafloor Bathymetry
This database is a 1 arc-minute global relief model with bathymetry derived from sea-surface satellite altimetry measurements and ocean soundings; topography is derived from GTOPO30. ETOPO1 utilizes bathymetry extracted from an older version of the estimated seafloor grid.
- SRTM30 Global Topography
The Space Shuttle Radar Topography Mission (SRTM) collected topographic height measurements between 56° S and 60° N during an 11-day mission in Feb 2000. NGDC (now NCEI) extracted non-zero values from 30 arc-second grids of the SRTM data for use in building ETOPO1; the SRTM grids contain "zero" values over the open ocean.
- Baltic Sea Bathymetry
The Leibniz Institute for Baltic Sea Research Warnemünde (IOW) has created two integrated bathymetric-topographic grids of the Baltic Sea: a roughly 2-km grid spanning the entire sea, and a roughly 1-km grid spanning the southwestern entrance to the sea. NGDC (now NCEI) extracted the bathymetric data for use in building ETOPO1.
- Caspian Sea Bathymetry
Bathymetric contours of the Caspian Sea were obtained from the Caspian Environment Programme. NGDC (now NCEI) gridded the contours using a tight spline tension to infill depths between contours. This grid was shifted 28 m vertically to be consistent with mean sea level before use in building ETOPO1.
- Great Lakes Bathymetry
NCEI, in cooperation with NOAA's Great Lakes Environmental Laboratory and the Canadian Hydrographic Service, has compiled detailed vector bathymetric contours and 3 arc-second (~90 m) bathymetric grids for most of the U.S. Great Lakes. This integrated bathymetric-topographic grid was extracted at 15 arc-seconds for use in building ETOPO1.
- Gulf of California Bathymetry
A previously created 7 arc-second grid of multibeam swath sonar bathymetric surveys in the mouth of the Gulf of California was used in building ETOPO. This grid is not currently available to the public, though all of the multibeam swath sonar bathymetry data can be obtained from NCEI's multibeam bathymetry database.
- IBCAO Bathymetry
The International Bathymetric Chart of the Arctic Ocean (IBCAO), is an integrated bathymetric-topographic grid. ETOPO1 incorporates bathymetry north of 65° N and Greenland topography from version 2.0, the most recent version.
- JODC Bathymetry
The Japan Oceanographic Data Center (JODC) has created 500-m bathymetric grids of the seafloor surrounding Japan, derived from a huge amount of depth-sounding survey data.
- Mediterranean Sea Bathymetry
The Mediterranean Science Commission (CIESM) has promoted the production of a morpho-bathymetric map of the Mediterranean Sea derived from multibeam swath sonar surveys. A 1-km grid of this data was graciously provided to NGDC by Benoit Loubrieu (Ifremer), which was used in building ETOPO1.
- U.S. Coastal Relief Model
The Coastal Relief Model (CRM) is a 3 arc-second (~90 m) grid that integrates land elevations and ocean depths, providing a comprehensive view of the U.S. coastal zone. The CRM covers the East and West Coasts, Gulf of Mexico, Hawaii and Puerto Rico. This integrated bathymetric-topographic grid was extracted at 15 arc-seconds for use in building ETOPO1.
Ice Surface Datasets
- Antarctica RAMP Topography
The National Snow and Ice Data Center (NSIDC) built a high-resolution digital elevation model of Antarctica's ice surface, derived from the Radarsat Antarctic Mapping Program (RAMP). NGDC (now NCEI) utilized the 400-m grid, version 2 in building the ETOPO1 Ice Surface grid.
- Antarctica BEDMAP Bedrock
The British Antarctic Survey has integrated all available Antarctic ice sheet data into a series of grids, including ice surface, ice thickness, bedrock, at 5-km cell size: the BEDMAP project. NGDC (now NCEI) resampled the bedrock grid to 1 arc-minute and used it in building the ETOPO1 Bedrock grid.
- Greenland NSIDC Bedrock
The National Snow and Ice Data Center (NSIDC) has built 5-km ice surface, ice thickness and bedrock elevation grids of Greenland. NGDC (now NCEI) utilized the bedrock grid, resampled to 30 arc-second cell size, in building the ETOPO1 Bedrock grid.
Two coastline data sets were used in evaluating individual source data sets and ETOPO1. They were also used to clip some data sets to the coastline to eliminate anomalous values.
- Antarctic Digital Database - a medium-resolution coastline for Antarctica, south of 60° S, created by the British Antarctic Survey. The database is managed by the Scientific Committee on Antarctic Research.
- GSHHS - GSHHS (Global Self-consistent, Hierarchical, High-resolution Shoreline) is a high-resolution shoreline data set amalgamated from two databases in the public domain. The data have undergone extensive processing and are free of internal inconsistencies such as erratic points and crossing segments.