Accuracy of the 2500 meter isobath from satellite bathymetry

The location of the 2500 m isobath is a key element in seabed territorial claims under the Law of the Sea. We examined the accuracy of the 2500 m isobath as shown in the "Bathymetry from Space" Version 8.2 product of Smith and Sandwell. This dataset is a two-arc-minute Mercator grid that combines ship soundings where available with topography interpolated from satellite gravity where there are gaps. We find the 2500 m isobath from the Smith and Sandwell satellite bathymetry grid meets International Hydrographic Organization (IHO) S-44 vertical (depth) accuracy standards 90% of the time in areas of smooth topography where good survey control data are available, but only 31% of the time in a rugged and poorly controlled area. A horizontal displacement of the satellite isobath with respect to the National Geophysical Data Center (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 bathymetry data.