Accuracy of the 2500 m Isobath from Satellite Bathymetry
Karen Marks(1) and Walter Smith(1)
Laboratory for Satellite Altimetry, E/RA 31,
Silver Spring, MD 20910,
In December 1994, ESA extended the ERS-1 Mission Phase F to collect complete geodetic coverage of the oceans with an 8-km ground track spacing. In 1995, the U.S. Navy released all the previously classified Geodetic Mission Data from Geosat. New maps of global ocean tectonics and seafloor topography were made possible thanks to these satellite missions.
Locating the 2500 m isobath is a crucial component of a Coastal State’s efforts to lay claim to its Juridical Continental Shelf under Article 76 of the United Nations Convention on the Law of the Sea. We compare depths from the altimetric bathymetry grid of Smith and Sandwell to depths surveyed by ships with multibeam acoustic echosounders to assess how accurately satellite bathymetry maps the 2500 m isobath. We find the satellite isobath meets IHO S-44 vertical accuracy standards 90% of the time in areas of smooth topography with good acoustic survey control, but only 31% of the time in a rugged, poorly surveyed area. A horizontal displacement of the satellite isobath with respect to the NGDC Coastal Relief Model offshore of New Jersey, USA, is due to the underlying depths being uncorrected for the velocity of sound in seawater in the Model and corrected in the satellite-derived bathymetry data.