J3527 : Slieve Donard Triangulation Pillar

3 km from Widows Row, Ireland

Slieve Donard Triangulation Pillar
Slieve Donard Triangulation Pillar
Trig pillar at the summit of Slieve Donard. The pillar is situated on the top of the stone tower as seen in J3527 : The summit of Slieve Donard. Donard was first triangulated in 1826 but this pillar was built for the re-triangulation of Northern Ireland c1950. It is officially called Slieve Donard (New) as readings couldn't be taken from the original station as the Mourne Wall (built c1910) blocked the cross-channel rays; therefore the new station had to be constructed on top of the tower to overcome this problem. Donard is one of the 12 Primary Stations established by the Ordnance Survey Northern Ireland for their re-triangulation. From here connections were made to other primary stations in Ireland - Divis, Trostan, Knocklayd, Sawel, Carrigatuke, Loughan Leigh, Castlecoe, Hill of Howth and Kippure; Donard is also a cross channel station and connections were made with Cairn Pat and Inshanks in Scotland, South Barrule on the Isle of Man and Holyhead in Wales. See J3527 : Flush Bracket, Slieve Donard Triangulation Pillar for a closer view of the flush bracket; pictures of the top of the pillar (the highest point in Northern Ireland) are impossible without a ladder!
OSNI Triangulation Stations
The re-triangulation of Northern Ireland by the Ordnance Survey Northern Ireland began in 1950. This was the first complete survey of Northern Ireland which included observations with the new primary triangulation of the country, its connection with the Republic of Ireland and the cross-channel connection between Ireland and Great Britain. This began by OSNI establishing a series of triangulation stations throughout the country. Almost all of these stations were topped by trig pillars and 80, mainly primary and secondary pillars, had been constructed by October 1949. Measurements between primary stations began in 1950 and measurements for these and the secondary stations were completed by July 1956. The construction and measurements for tertiary stations were completed later (probably no later than the mid 1960s). Only two stations are not topped by pillars - Lighthouse Island, marked by a brass rivet, and Ardglass, which utilised the top of a high stone folly. The older triangulation stations on the Lough Foyle Base Line were also re-surveyed as part of this process. A majority of the stations are still extant today but a few have been removed or destroyed.
The Mourne Wall
The Mourne Wall is a 22 mile long wall in the Mourne Mountains. It was built between 1904 and 1922 by the Belfast Water Commissioners to enclose their water catchment areas in the Mournes and protect the area from the effects of cattle and sheep on the water course. The wall is predominately constructed from local granite stone using traditional dry stone walling techniques; on average the wall is about 1.5 metres high and 0.8 to 0.9 metres thick. It is not uniform in construction along the entire length - the 'classic' granite wall is only to be found north of Carn mountain and Long Seefin with particularly impressive sections on Slieve Commedagh and Slieve Donard; elsewhere the wall largely resembles dry stone walls found elsewhere in the Mournes and south County Down. In places, such as Slieve Muck, the wall is not constructed of granite at all.
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year taken
2012
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J3527, 62 images   (more nearby)
Photographer
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Image classification?
Supplemental image
Date Taken
Saturday, 11 August, 2012   (more nearby)
Submitted
Monday, 13 August, 2012
Geographical Context
Historic sites and artefacts  Uplands 
Place (from Tags)
Mourne Wall  Mourne Mountains  Slieve Donard  Triangulation Station 
Subject Location
Irish: geotagged! J 35787 27685 [1m precision]
WGS84: 54:10.8121N 5:55.2596W
Photographer Location
Irish: geotagged! J 35787 27685
View Direction
Northeast (about 45 degrees)
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