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Articles

1979: Vol. LVI, No. 1

A Uniform Tidal Datum System for the United States of America

Submitted
August 7, 2015
Published
2015-07-10

Abstract

The tidal datum of Mean Lower Low Water will be adopted as Chart Datum for all nautical charts, bathymetric maps, and tide tables of the National Ocean Survey. The Mean Higher High Water Line will be depicted as the Shoreline on all nautical charts and bathymetric maps. The low water line, when called for on large-scale charts with broad beach slopes, will be the Mean Lower Low Water Line. Legal difficulties may require the retention (as it did for creation) of Gulf Coast Low Water Datum and the establishment of Gulf Coast High Water Datum. However, these datums lie at the elevations of Mean Lower Low Water and Mean Higher High Water, respectively, in a regime of alternating mixed and diurnal tides. Implementation will probably require six years. Accuracies will be consistent with present practices.