World Heritage Photos

Struve Geodetic Arc – Triangulation Points Across the Baltic States

The Struve Geodetic Arc is a chain of 265 triangulation survey stations. The Struve Geodetic Arc stretches from Hammerfest in Norway to a station point close to the Black Sea in Ukraine; it passes through ten countries and over 2,820 km. The chain was established and used by the astronomer Friedrich von Struve to determine the exact shape and the size of the Earth. Struve carried out his triangulation measurements between 1816 and 1855.

The Struve Geodetic Arc is an extraordinary example of scientific cooperation between different countries. The Tähetorn Observatory is a station point of the Struve Geodetic Arc at Tartu in Estonia. The astronomer Friedrich von Struve was director of the Tartu Tähetorn Observatory from 1820 to 1839. One of the station point of the Struve Geodetic Arc in Lithuania is located near Meškonys, a small village not far from Vilnius.

The UNESCO World Heritage Site includes 34 of the station points, with different markings, such as drilled holes in a rock, iron crosses, obelisks and buildings. The Tartu Tähetorn in Estonia and Alatornio Church in Finland are the only buildings that were used for the measurements. The 34 station points of the Struve Geodetic Arc were declared a UNESCO World Heritage Site in 2005. 

Work of Art: Friedrich von Struve.

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   Geodetic Arc of Struve: A monument in Tartu to commemorate the station point and the Arc of Struve. The Geodetic Arc was established and used by the astronomer and geodesist Friedrich von Struve to determine the exact shape and size of the Earth. The northernmost point of the Geodetic Arc is situated near Hammerfest in Norway; the southernmost point is situated close to the Black Sea in Ukraine. Friedrich Georg Wilhelm von Struve conducted most of his research in the Tartu Old Observatory of the University of Tartu in Estonia. This observatory was active from 1802 to 1964. Today, the historic building serves as a museum.

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   The Old Observatory in the town of Tartu in Estonia is one of the most important station points of the Struve Geodetic Arc. Friedrich von Struve was director of this observatory (Tähetorn) from 1820 to 1839. The observatory was built at the beginning of the 1800s. The first heyday of the observatory started in 1813 when this widely-known astronomer and geodesist began working here. The size and shape of the Earth were calculated using triangulation based on the survey points of the Geodetic Arc. The arc consists of a chain of 265 triangulation survey stations and stretches across ten countries and over 2,820 kilometres. 

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   An information board about the Struve Geodetic Arc at the former Tartu Old Observatory in Estonia. This arc was used to determine the precise shape and size of the Earth; a basis for making more accurate world maps. Out of the 265 triangulation survey stations, only 34 station points were inscribed on the UNESCO World Heritage List in 2005 as a joint site. The Tartu Old Observatory in Estonia and the Alatornio Church in Finland are the only buildings that were used for the measurements. Other markings are, for example, iron crosses, drilled holes in rock and obelisks, built especially for this purpose.

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   During a road trip through the Baltic States in our 1974 classic Mini, we passed through Meškonys, a village in Lithuania. Standing there was an obelisk marking one of the survey points of the Struve Geodetic Arc. Although the measurements were taken between 1816 and 1855, they proved to be remarkably accurate. Using the simple instruments of the time, Friedrich von Struve calculated the Earth's equatorial radius to be just over 6,378 kilometres; this figure was only 224 metres greater than calculations based on modern NASA satellites. For this reason, the arc is regarded as one of the greatest scientific and cartographic triumphs in human history.