Great Arc of the Indian meridian
Gran Arco del Meridiano de la India
- Date
- 1802-1841 · confidence high
- Place
- St Thomas Mount, Chennai, Tamil Nadu, India
- Credited to
- William Lambton and George Everest (Great Trigonometrical Survey)
- People
- 👤 George Everest1790–1866👤 William Lambton1756–1823
- Field
- Cosmos & Earth
What was discovered
Triangulation survey of a meridian arc of about 2,400 km from Cape Comorin to the Himalayas, the largest geodetic measurement of its time. It refined the shape of the Earth and served as the skeleton for mapping the subcontinent.
The deflection of the plumb line near the Himalayas detected in the arc led Pratt and Airy to formulate the theory of isostasy (1855).
What it led to
- precise values for the Earth's flattening (Everest ellipsoid)
- modern cartography of South Asia
- discovery of gravitational anomalies in the Himalayas (isostasy)