The Arc of the 30th Meridian Recognised in South Africa in June 2004

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The unveiling of the plaque by Colin Bollaert-Davies, President of the Institute of Professional Land Surveyors of the Eastern Cape

The Arc of the 30th Meridian is known to surveyors worldwide as a triangulation system that stretches from South Africa northwards all the way to Cairo. On 8 June 2004 a plaque was unveiled on the southern terminal beacon at Buffelfontein in the Eastern Cape of South Africa to commemorate the 125th anniversary of when the idea of such an Arc was conceived and the 50th of its completion.

It was the idea of David Gill when he arrived in South Africa as Her Majesty's Astronomer at the Cape of Good Hope in 1879.

Among his very first actions was to pursue with the Governor and others the thought of a Cape to Cairo Arc. Within a matter of just a few years work was under way and by 1910 had been completed to about 9º South. After slow and piecemeal progress by 1950 the whole arc had been completed except for a 1000 km in Northern Uganda/Southern Sudan where the Sudd area was a barrier to traditional survey methods. In 1953-4 the US Army Map Service arrived in force and closed the gap. This was soon followed by the US Air Force, who in 1954 in cooperation with the Greek Army Geographical Service and the Survey of Egypt, observed a Hiran connection from North Africa (Egypt and Libya) to Crete across the Mediterranean Sea.

Thus it was that part of Gill's "Dream" came into being after 75 years of survey work. However by 1900 Gill had extended his original dream to the idea of an Arc from "Cape to Cape" meaning Cape Colony to North Cape in Norway. Evidence suggests that although not in way thought of by Gill, the extension of the Arc from Crete to North Cape can be proved through work carried out at several different periods from 1816 to 1855 and in the period between the Great Wars.

The beacon at Buffelsfontein witnessed a group of surveyors gathered in showery weather in a most picturesque area outside of Port Elizabeth to watch Colin Bollaert-Davies, the President of the Institute of Professional Land Surveyors of the Eastern Cape, unveil the plaque on a refurbished beacon of the Geodetic Survey of South Africa. It is the hope of the local surveyors that it will prove possible for the beacon to be recognised as a national monument since there are precedents for such in the Cape Town area.

Any readers, particularly in the countries through which the arc goes, who are interested in the 30th Arc are welcome to contact Jim Smith at

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The plaque. The text on the plaque is as follows:
This beacon represents the Southern most point of a chain of triangles Measured along the 30th meridian through Botswana, Mozambique, Zimbabwe, Zambia, Tanzania, Burundi, Uganda, the Democratic Republic of Congo, Sudan and ending near Cairo in Egypt. The purpose of the measurement was to determine the size and shape of the Earth. Prior to 1999 the beacon was also the origin of the geodetic survey of South Africa.
The project was initiated by Sir David Gill, the Astronomer Royal at the Cape in 1879 and the final measurements were completed in the Sudan 1954.
The arc, known as the Arc of the 30th Meridian, can be connected across the Mediterranean Sea through Crete and Belarus to a similar arc measured through Europe terminating at North Cape in Norway. The European arc is known as the Struve Arc and together these two arcs cover nearly 105º in latitude which is over 11650 Km in length.
This plaque was unveiled by the President of the Institute of Professional Land Surveyors of the Eastern Cape, Mr C J Bollaert-Davies, on 8 June 2004, 125 years after the initiation of the project and 50 years after the completion of measurements.

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Map of the whole of the 30th Arc. Reproduced courtesy of T. Zakiewicz