A mareograph is an automatic equipment for measurement of water level variations. If the installation is in an inland sea, it is called a limniograph.

The mareograph on the photo is made following the example of Pola in Austria- Hungary. The instrument was used by SMHI and its predecessor during the years 1886 to 1966. The cost of production in 1886 was 545 Swedish crowns. The disc with chart paper (mareogram) serves as plumb to the movement. Sea level change is transmitted from the float via rail, chain, wheel and rack to the left the pen. The right pen marks every whole hour.

Mareograph used by SMHI 1886-1966 Foto Thomas Hammarklint Förstora Bild

After a state visit to Prussia it was decided by the Swedish King Oscar II
that a number of mareographs would be built around the Swedish coast.
Later ten mareographs were installed inside the classic octagonal house
in the following places: Ratan, Furuögrund, Draghällan, Björn, Stockholm-
Skeppsholmen, Landsort, Kungsholmsfort, Ystad, Varberg and Smögen.

Sea level values ​​from the mareograms are transferred into digital form
and are stored today in a database at SMHI.