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NON-EXISTENT SEAMOUNTS. A CASE STUDY
NAVAL OCEANOGRAPHIC OFFICE NSTL STATION MS
Attempts to pinpoint some of the shallow underwater features shown on nautical charts have failed. Some of these features appear to be non-existent. An evaluation of these indicates that many were found using shallow water echo sounders, which were run intermittently in deep water. The depths reported represent either a shallow scattering layer or a bottom of varying reflector character at greater depth. Difficulty in determining the phase in which the recorder was operating prevents an accurate determination of either the type or the depth of the reflector surface. The American Scout Seamount, reported 700 miles east of Newfoundland in the North Atlantic Ocean, is presented as a feature typical of those that cannot be found. Data assembled to evaluate this feature also point up the need for an investigating technique of a reconnaissance nature if non-existent feature or features positioned more than 30 nautical miles in error are to be conclusively eliminated from hydrographic data. Removal of non-existent features from nautical charts is dependent on the international agreement of standards and procedures to be used in conducting the reconnaissance and detail surveys and the publication of the results of these surveys in official international journals or through official Notices to Mariners.
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