Bench Mark :: Shared Description

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 Due to updated mapping techniques and technological advances such as GPS, bench marks are no longer maintained.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.
by Rossographer
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3381 images use this description. Preview sample shown below:

SK1746 : Bench mark, 1 Church Street, Ashbourne by Alan Murray-Rust
J5081 : Bench Mark, Bangor by Rossographer
SP2092 : OS benchmark - Lea Marston, St John's church by Richard Law
SO8611 : Milestone & Benchmark, A46 by Mr Red
SE6132 : Bench mark, #13/15 Flaxley Road by Alan Murray-Rust
SP2377 : OS benchmark - Balsall Common, 299 Kenilworth Road by Richard Law
NT2473 : Bench mark, 125 George Street, Edinburgh by Alan Murray-Rust
SJ9515 : OS benchmark - Teddesley Park, gatepost near Keeper's Pools by Richard Law
SK7250 : Bench mark, Morton Grange by Alan Murray-Rust
SK0101 : OS benchmark - Harden, shops at roundabout by Richard Law
SP1484 : OS benchmark - Gilbertstone, 60 Brays Road by Richard Law
SJ5204 : Milestone at Pitchford Park by Richard Law
NT0804 : OS Flush Bracket G478 - Moffat by Richard Law
SJ7009 : OS cutmark - Telford, cycleway beside Queensway by Richard Law
TG4918 : OS Flush Bracket at Mill Farm by Richard Law
SK0001 : OS benchmark - Blakenall Heath, 9 Chantry Avenue by Richard Law
NS6065 : Fundamental Bench Mark, Glasgow by Rossographer
SS2006 : OS benchmark - Bude, porch on The Castle by Richard Law
SP1585 : OS benchmark - Garretts Green, 14 Clopton Road by Richard Law
SP2080 : OS benchmark - Hampton in Arden church by Richard Law
SU6784 : Bench mark, St John's Church, Stoke Row by Alan Murray-Rust
SK8170 : Bench mark at Marshgate Farm by Alan Murray-Rust
SP3066 : Bench mark, St Mark's Road by Alan Murray-Rust
SK4738 : Footpath to Stanton village by Alan Murray-Rust
SJ9003 : OS pivot mark - Fordhouses, Marsh Lane bridge by Richard Law

... and 3356 more images.

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Created: Tue, 2 Mar 2010, Updated: Tue, 14 Jun 2016

The 'Shared Description' text on this page is Copyright 2010 Rossographer, however it is specifically licensed so that contributors can reuse it on their own images without restriction.