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A Full-Color Poster National Geophysical Data       Center and World Data Service for       Geophysics, BoulderAnnouncement 97-MGG-03 by       W.H.F.Smith* and D.T. Sandwell** 

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* NOAA / Satellites       and Information / ORA / Laboratory for       Satellite Altimetry ** Univ of California, San Diego / Scripps Institution of       Oceanography / Institute       of Geophysics & Planetary Physics
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A new color poster has been prepared displaying measured and estimated       seafloor topography. The poster is printed in a Mercator projection from       data gridded uniformly at intervals equivalent to 2 minutes longitude at       the equator. This new estimate of seafloor topography was obtained from       shipboard depth soundings combined with gravity data derived from       satellite altimetry to produce a gridded representation of seafloor       topography for all ice-free ocean areas within +/-72 degrees latitude. The       depth data were obtained by screening 6905 surveys from the NGDC (Marine       Trackline Geophysics CD-ROM version 3.2), the Scripps Institution of       Oceanography and Lamont-Doherty Earth Observatory databanks, and other       data, using quality control procedures based on those of Smith [J.       Geophys. Res. 98, 9591-9603, 1993]. The satellite gravity field combines       all data from the ERS-1 and GEOSAT satellites including the data       declassified in 1995; it has an RMS accuracy of 3-5 mGal and a resolution       of 20-30 km wavelength [Sandwell and Smith, J.Geophys. Res. 102,       10,039-10,054, 1997]. 

The method [Smith and Sandwell, Science 277, 1956-1962, 1997] is an       improvement on one developed earlier for GEOSAT data south of 30 degrees S       [Smith and Sandwell, J. Geophys. Res. 99, 21,803-21,824, 1994]. The new       topographic map is visually quite different from the satellite gravity       field. Isostatically compensated topography stands out in full relief, and       edges are sharper due to the inclusion of ship data and the       downward-continuation of the gravity field. Dramatic scarps are seen such       as at the eastern edge of Manihiki Plateau. The topography map shows       seafloor structure while the gravity map includes sub-seafloor anomalies.       In addition to this poster, digital data will be available at a later date       on CD-ROM. The disc will contain the 2x2 minute digital data for the       Measured & Estimated Seafloor Topography as binary raster files and       formatted for use in GMT (Generic Mapping Tool). The GEOSAT gridded       2-minute gravity data will also be on the CD-ROM. 
On-line related       imagery - September 25, 1997More       information on predicted topography, on-line images, and related data and       posters available from Scripps and NGDC
Measured & Estimated Seafloor Topography       Poster, WDC GMG, Boulder RP-1 A color poster approximately       34" X 53"Product number G01333-POS-A0001

Also see: ETOPO2       CD-ROM

The official bibliographic citation for this product is:       
Smith, W., and Sandwell, D., 1997, Measured and Estimated       Seafloor Topography, World Data Service for Geophysics, Boulder Research       Publication RP-1, poster, 34" X 53". NGDC home | disclaimers | questions Website of the US Dept of Commerce/NOAA/NESDIS/NGDC