The average height of all high tide water levels measured over an 18.6 year period is known as what?

The average height of all high tide water levels measured over an 18.6 year period is referred to as the mean high water. This term represents the average of the high water heights recorded during the specified timeframe. It is significant in coastal surveying as it helps to establish baseline elevations for mapping and engineering projects and is essential for understanding tidal influences on coastlines.

Other options do not correctly represent this concept. High tide median, for instance, does not have a standard definition in tidal studies and would not generally be used in this context. Standard tidal height could imply a variety of heights without specifically indicating an average or mean measurement, while highest mean tide suggests a different calculation focusing on the maximum average rather than the overall average height. Therefore, mean high water is the most accurate term in this context.