Question 2002Navigation General

The correct answer is C) mean sea level. Mean sea level (MSL) is the average height of the surface of the sea for all stages of the tide over a 19-year period, as defined by the National Oceanic and Atmospheric Administration (NOAA). This 19-year period is known as the National Tidal Datum Epoch, which is the time period used to determine the official tidal datums in the United States. The other options are incorrect because they represent different tidal datums: mean low water (A) is the average of all the low tides, half-tide level (B) is the average of the mean high water and mean low water, and mean high water (D) is the average of all the high tides, rather than the overall average height of the sea surface over the 19-year period.