Joan of Arc | Meridian | Meridian, Mississippi | Arc de Triomphe | meridian | L'Arc-en-Ciel | ITV Meridian | ARC | 97th meridian west | The Passion of Joan of Arc | story arc | Blood Meridian | 144th meridian east | 114th meridian west | Prix de l'Arc de Triomphe | Meridian (geography) | Fort Jeanne d'Arc | Joan of Arc (1948 film) | Arc of Infinity | Arc lamp | 57th meridian west | 125th meridian west | 105th meridian west | 104th meridian west | Arc Angels | 6th meridian east | 153rd meridian east | 115th meridian west | 105th meridian east | 103rd meridian west |
Together with ʿAlī ibn ʿĪsā al-Asṭurlābī in 827, he measured at 35 degrees north latitude, in the valley of the Tigris, the length of a meridian arc and thus the Earth's circumference, getting a result of 40,248 km (or, according to other sources, 41,436 km).
In 1744, La Condamine, in charge of the expedition sent to Peru in 1735 to determine the length of a degree of the meridian arc in the neighbourhood of the equator, passed by and gave his name to one of the mountains behind Kourou.
The most notable expedition (1736–1737) was led by a member of the Académie française, Pierre Louis Moreau de Maupertuis, who came to take meridian arc measurements along the Torne River Valley which would show that the globe is flattened towards the poles.