From LaCaille to Gill and the start of the Arc of the 30th Meridian
Smith, Jim R.
If one looks at a map of European arcs of meridian and parallel at the beginning of the 20th century there will be seen to be a plethora them. Turning to Africa there was the complete opposite. Other than the arcs of Eratosthenes (c 300 BC) and the short arcs by LaCaille (1752) and Maclear (1841-48) the continent was empty. It was in 1879 that David Gill had the idea for a Cape to Cairo meridian arc but 1954 before it was completed. This presentation summaries the work of LaCaille and Maclear and then concentrates on a description of the 30th Meridian Arc in East Africa. The only other comparable arcs at the time were that through the centre of India by Lambton and Everest observed between 1800 and 1843; the Struve arc of 1816 to 1852 and the various arcs in France during the 18th century. The usefulness of such arcs was highlighted in 2005 with the inscription by UNESCO of the Struve Geodetic Arc on the World Heritage Monument list. A practical extension to the Struve Arc Monument is the 30th Meridian Arc since there is a connection between the two.
Event: XXIII International FIG Congress : Shaping the change
Only personal, non-commercial use of this document is allowed.