Visual tide pole

Until 1910 heights of the visual tide poles were measured and, after establishment of a chart datum, recalculated. From around 1920 datum of the visual tide poles has been measured approximately every third year by the National Survey and Cadastre. 

Visual Tide Pole where an observer read the pole. This simple method enables relative... 

Datum, benchmarks on land and benchmark on the Visual Tide Pole are established and maintained by the National Survey and Cadastre. 

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