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Struve Geodetic Arc

Cultural criteria: ii, iv, vi
Year of inclusion in the List of World Heritage: 2005

“The Struve Arc” (“Russian-Scandinavian Arc”) is a chain of old triangulation points extending for 2,820 km on the territory of ten European countries and representing a unique monument of science and technology.

The “Arc” oriented from north to south and going approximately along the 25th meridian of east longitude, originates from the “Fuglenes Point” lying on the shores of the Barents Sea, close to the Norwegian city of Hammerfest (in latitude 70° North), then it goes southward – through another eight countries of Northern and Eastern Europe (a little eastward of Helsinki, Tallinn, Riga and Vilnius, and considerably westward of Minsk and Kiev, then near Kishinev), and ends not far from the Black Sea Coast, in the frontier south-west of Ukraine, near Ishmael– the “Staro-Nekrasovka Point” (in latitude 45° North).

These geodesic points of sight were installed in the period of 1816-1855. Works were carried out under the direction of the well-known Russian astronomer and geodesist of those times – Friedrich Georg Wilhelm (Vasily Yakovlevich) Struve, 1793-1864, academician of St. Petersburg Academy of Sciences, founder and the first director of the Pulkovo Observatory.

Field investigations proper were carried out by Carl Tenner, 1783-1859 – military geodesist, colonel, and afterwards lieutenant general. Tenner was accompanied by a group of assistants, guides and soldiers.

Thus, Struve made the first reliable measurement of the big segment of the Earth meridian’s arc. It enabled him to exactly determine our planet’s dimension and form, which became an important step in the development of Earth sciences and advanced much the whole industry of topographic mapping. Following the results of his investigations and upon completion of all calculations Struve wrote a big work – “The Meridian Arc at 25 20' between the Danube and the Arctic Ocean Measured between 1816 and 1855”

Those measurements’ accuracy proved to be quite astonishing – the modern satellite “verification” of the technology, applied by Struve more than 150 years ago, gave insignificant difference. But for those days it was not only the most exact, but also the most grandiose grid measurement of Earth: because a huge section was covered in latitude – approximately of 25 degrees (or 1/14 of the earth circle). Those measurements results during the whole century (until satellite methods in geodesy appeared, already in the middle of the XX century) were used when calculating parameters of the Earth ellipsoid.

Originally the “arc” consisted of 258 geodesic “triangles” (polygons), adjoining each other and lined up from north to south in a peculiar “chain” with 265 main triangulation points, situated in the corners of these “triangles”. But not all of the original points were discovered during special search and geodesic works, undertaken in recent years with the active cooperation of scientists from interested countries, and, moreover, many of them turned out to be in terrible dilapidation. That is why the World Heritage Site has included only the most intact points – in all 34 (particularly in Byelorussia – 5 points, in Ukraine – 4, in Russia – 2, in Moldavia – 1). Both Russian triangulation points are situated on the small Hogland Island in the Gulf of Finland – they are the “Maki-Paalys Point” and “Z Point”.

Control points of this triangulation network were marked on the ground in different ways, namely: Pricks hollowed out in rocks, iron crosses, stone pyramids, or specially installed obelisks. Such a point was often marked by a sandstone brick, laid in the bottom of a hole, or it was a granite cube with a cavity filled with lead and put in a hole of cobble-stones. Nowadays this ancient marking is being renewed, in the old triangulation points special signs are installed.

“The Struve Arc” is a unique element of the World Heritage List indeed: firstly, because it is the only – in the whole List – “concerning the interests” of so many states (in all 10), secondly – because before 2005 the List had no sites so closely related to problematics of geodesy and cartography.