J0826 : Bench Mark, Newry

taken 4 years ago, near to An Tiur, Northern Ireland

Bench Mark, Newry
Bench Mark, Newry
Bolt bench mark on the northern parapet of the Sugar Island bridge across the Newry River (also the County Boundary between Armagh and Down). It consists of a cut mark with a copper bolt driven into the parapet and dates from the 1st geodetic levelling of Ireland which took place in 1839-43. It is both the 154th mark in a line of 298 which stretches from Dublin (starting at Buckingham Lock LinkExternal link ) to Belfast (ending at J3474 : Bench Mark, Belfast) and the 1st in a line of 43 from Newry to Armagh. The original remarks describe it as a "Copper bolt driven into N. battlement of Sugar Island Bridge in Newry; 1.7 feet above centre of road" and it was originally levelled to 25.768 feet above sea level.
Today the mark has been levelled to 5.13 metres above MSL.

There are two more 1GL bolts nearby in Newry: one on the front of the RC church in John Mitchel Place, but the gate was locked and I had no long lens with me! It can be seen at LinkExternal link ; the other is on the Cathedral which I forgot about, but it can be seen at LinkExternal link .
Bench Mark
Bench marks were historically used to record the height above sea level of a location as surveyed against the Mean Sea Level data (taken at Clarendon Dock, Belfast, for Northern Ireland data, Newlyn in Cornwall for data in Great Britain and Portmoor Pier, Malin Head, for data relating to the Republic of Ireland). They were used as part of a greater surveying network by the UK Ordnance Survey, Ordnance Survey Northern Ireland (OSNI) and the Ordnance Survey Ireland (OSI). If the exact height of one bench mark is known then the exact height of the next can be found by measuring the difference in heights, through a process of spirit levelling. In this way hundreds of thousands of bench marks were sited all around the UK & Ireland from the mid 19th to late 20th centuries. There are several distinct types of bench mark:

- Fundamental bench marks have been constructed at selected sites where foundations can be set on stable strata such as bedrock. Each FBM consists of a buried chamber with a brass bolt set in the top of a granite pillar. See NG8825 : Dornie fundamental bench mark for an example. FBMs were used in Ireland as well as GB but those in Ireland do not have any surface markers, nor are they marked on standard maps.
- Flush brackets consist of metal plates about 90 mm wide and 175 mm long. Each bracket has a unique serial number. They are most commonly found on most Triangulation Pillars, some churches or on other important civic buildings. See J3270 : Flush Bracket, Belfast for an example.
- Cut bench marks are the commonest form of mark. They consist of a horizontal bar cut into a wall or brickwork and are found just about anywhere. A broad arrow is cut immediately below the centre of the horizontal bar. See J3372 : Bench Mark, Belfast for an example. The horizontal mark may be replaced by or contain a bolt - see J1486 : Bench Mark, Antrim.
Other marks include:
- Projecting bench marks such as SD8072 : Projecting Bracket Benchmark on St Oswald's Tower
- Bolt bench marks such as SJ1888 : OSBM bolt on Hilbre Island
- Rivet bench marks such as J3978 : Bench Mark, Holywood
- Pivot bench marks such as SJ2661 : Pivot bench mark on Leeswood Bridge

Bench marks are commonly found on older buildings or other semi-permanent features such as stone bridges or walls. Due to updated mapping techniques and technological advances such as GPS, bench marks are no longer maintained. Many are still in existence and the markers will probably remain until they are eventually destroyed by redevelopment or erosion.
Creative Commons Licence [Some Rights Reserved]   © Copyright Rossographer and licensed for reuse under this Creative Commons Licence.
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J0826, 696 images   (more nearby )
Photographer
  (find more nearby)
Date Taken
Wednesday, 4 December, 2013   (more nearby)
Submitted
Sunday, 8 December, 2013
Geographical Context
Historic sites and artefacts  City, Town centre 
Place (from Tags)
Newry 
Subject Location
Irish: geotagged! J 086 267 [100m precision]
WGS84: 54:10.6686N 6:20.1878W
Camera Location
Irish: geotagged! J 086 267
View Direction
Northeast (about 45 degrees)
Clickable map
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Other Tags
Newry  OSNI  Benchmark Site  Ordnance Survey Bench Mark  Bench Mark  1GL  Cut Bench Mark  Bolt Bench Mark  Bridge  Sugar Island Bridge 

Click a tag, to view other nearby images.

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