ordnance datum

British

noun

OD. mean sea level calculated from observation taken at Newlyn, Cornwall, and used as the official basis for height calculation on British maps

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Example Sentences

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A bench mark at some known height above ordnance datum should be set up in the hut, preferably on the top of the tube.

From The Sewerage of Sea Coast Towns by Adams, Henry C.

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023