|Gravity Field Over the S.Ocean - Poster, MGG-6
|This is a full color 24 by 36 inch poster. In many areas of the global ocean, the
depth of the seafloor is not well known because survey lines by ships are hundreds
of kilometers apart. Satellites carrying radar altimeters have measured the shape
of the ocean along tracks only 3-4 km apart, and from these data we can make very
accuratore (+/-3mGal) and high resolution (15km) maps of the marine gravity field.
The gravity field mimics the seafloor topography in the 15-160 km wavelength band
if sediment cover on the ocean floor is thin. Long-wavelength (greater than 160 km)
topography is isostatically compensated and is not correlated with the gravity field.
In addition, the satellite gravity field and the available depth measurements were
used to determine the correlation between gravity and the seafloor topography. By
applying this correlation to the gravity field we predict seafloor topography in the
15-160 km wavelength band. This topography is combined with a long-wavelength component
estimated directly from ship depth measurements. The result reveals many new features
and is within +/- 100m of actual depths in many cases. The Predicted Seafloor Topography
derived from the depths estimated from Satellite Altimetry in combination with measured
trackline bathymetry is an inferred data set and is not true bathymetry. It is, however,
the best estimate of seafloor topography available resulting from satellite gravity
data and actual ship depth measurements. These data are intended for scientific research
and should not be used for navigational purposes. Additional software is required
in order to manipulate the data or produce your own graphic images. Poster and CD-ROM
products are available for both gravity anomaly and estimated seafloor topography
of several regions. Please refer to URL http://www.ngdc.noaa.gov/mgg/announcements/announce_predict.html
for more information, and to download sample images.