datum. This datum is fixed at the level of the lowest predicted tide, or LAT (Lowest Astronomical Tide), as the prediction is made using astronomical tide-generating forces. The LAT ignores adverse weather conditions, such as high winds, which can cause a lower tide than LAT (ie, the LAT assumes average meteorological conditions).
All hydrographic charts for navigation are reduced to this chart datum for obvious reasons. However, for global sea-level determination (perhaps by satellite) the sea height will possibly be referenced to a different
datum, such as a reference ellipsoid, as I think may have been the case in determining the slope (sea) between England and France. But that is another
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