Sea Level at Gedser and Hornbaek

With the aim of publication in this book, the gauge data of Gedser and Hornbaek from 1890 to 1972 were digitized and calibrated in cooperation between DMI, lOW, and BSH. Later data were provided digitally by DMI. 

In the end of the nineteenth century the Danish Meteorological Institute (DMI) established 10 tide gauge stations scattered along the Danish coast with this only objective To calculate and define a national reference level (Chart damm). This network of stations was in the twentieth century supplemented with additional stations (more or less permanent in time and location) resulting in a present network of 15 stations. 

Until around 1970 the instruments were connected to a pen recorder where continuous measurements were drawn on analogue charts. Afterward hourly values were manually extracted and written on papers. Around 1970 the pen recorder was replaced with a potentiometer and a paper tape puncher enabling automatic transfer of data to a computer at DMI afterward. Around 1990 all stations changed to automatic real-time data transmission allowing online communication of data to a computer at DMI. 

All tide gauges have been attended almost daily by a trained observer, who has collected ancillary tide gauge information. 

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. 

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