Talk:Chart datum

Physics: Fluid Dynamics Stub‑class Low‑importance

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"Mean Spring High Tide"

In the UK, heights above sea level use the "mean spring high tide" level as their datum. This I hope needs no further definition, its meaning appears obvious to the undersigned Brit. But the US terms "mean high water" and "mean higher high water" are not obvious. Could they be defined in the article? Also it would be useful to know how they relate to "mean spring high tide". Maproom (talk) 13:45, 29 September 2009 (UTC)[reply]