First Day Cover
首日封
Sobrescrito de 1.º Dia
EstoniaThe Struve Geodetic Arc
Date of Issue : 6 May 2011
The Struve Geodetic Arc is a chain of survey triangulations stretching from the Black Sea to Norway’ northern coast on the initiative of Friedrich Georg Wilhelm Struve (1793-1864) for the measurement of the shape and size of the planet Earth. The length of the arc is 2,820 km. When the arc was created and more than a century later it was the longest measured meridian arc. It passes through the territory of today’s Norway, Sweden, Finland, Russia, Estonia, Latvia, Lithuania, Belarus, Moldova and Ukraine. The original arc consisted of 258 main triangles and 265 main station points. Thirty-four of the original station points today survive, and three of them are situated in Estonia, one in the Tartu Observatory and two in Simuna in the West-Viru County. Since 2005 the Struve Geodetic Arc is a UNESCO world heritage site.
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