Mean sea level: Difference between revisions

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|Meaning=(Abbreviated MSL; popularly called sea level.) The [[arithmetic mean]] of hourly  heights observed over some specified period.
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|Explanation=In the United States, mean sea level is defined as the mean height of the surface of the sea for  all stages of the [[tide]] over a 19-year period. Selected values of mean sea level serve as the sea level  [[datum]] for all [[elevation]] surveys in the United States. In meteorology, mean sea level is used as  the reference surface for all altitudes in upper-atmospheric work; in aviation it is the level above  which [[altitude]] is measured by a [[pressure altimeter]]. Along with [[mean high water]], [[mean low water|mean low  water]], and [[mean lower low water]], mean sea level is a type of tidal datum. <br/>''Compare'' [[half-tide level|half-tide  level]], [[still-water level]].
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== mean sea level ==
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<div class="definition"><div class="short_definition">(Abbreviated MSL; popularly called sea level.) The [[arithmetic mean]] of hourly  heights observed over some specified period.</div><br/> <div class="paragraph">In the United States, mean sea level is defined as the mean height of the surface of the sea for  all stages of the [[tide]] over a 19-year period. Selected values of mean sea level serve as the sea level  [[datum]] for all [[elevation]] surveys in the United States. In meteorology, mean sea level is used as  the reference surface for all altitudes in upper-atmospheric work; in aviation it is the level above  which [[altitude]] is measured by a [[pressure altimeter]]. Along with [[mean high water]], [[mean low water|mean low  water]], and [[mean lower low water]], mean sea level is a type of tidal datum. <br/>''Compare'' [[half-tide level|half-tide  level]], [[still-water level]].</div><br/> </div>
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Latest revision as of 10:48, 29 March 2024

(Abbreviated MSL; popularly called sea level.) The arithmetic mean of hourly heights observed over some specified period.

In the United States, mean sea level is defined as the mean height of the surface of the sea for all stages of the tide over a 19-year period. Selected values of mean sea level serve as the sea level datum for all elevation surveys in the United States. In meteorology, mean sea level is used as the reference surface for all altitudes in upper-atmospheric work; in aviation it is the level above which altitude is measured by a pressure altimeter. Along with mean high water, mean low water, and mean lower low water, mean sea level is a type of tidal datum.
Compare half-tide level, still-water level.

The level of the sea after averaging out the short-term variations due to wind waves.

Any function of time f(t) is periodic with period t if f(t) = f(t + τ) for all times t, where τ is the smallest number for which this equality holds.

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