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 Due to updated mapping techniques and technological advances such as GPS, bench marks are no longer maintained.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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3000 images use this description. Preview sample shown below:

J5180 : Bench Mark, Bangor by Rossographer
SK8810 : Bench mark, Holy Cross Church, Burley on the Hill by Alan Murray-Rust
ST5578 : Bench Mark, Blaise Castle near Bristol by Rossographer
SP2077 : OS benchmark - Barston, footbridge over the Blythe by Richard Law
SD1780 : OS benchmark - Millom, old Town Hall by Richard Law
SK4832 : Bench mark, Sawley railway bridge by Alan Murray-Rust
SD1580 : OS benchmark - Haverigg, wall on the A5093 by Richard Law
SK2327 : Bench mark, Rolleston Church by Alan Murray-Rust
SK7881 : Bench mark, All Saints' Church, South Leverton by Alan Murray-Rust
SK6233 : Gatepost with bench mark, Clipston Lane by Alan Murray-Rust
SO9198 : OS benchmark - the former Tiger Hotel by Richard Law
SJ6904 : OS benchmark - Madeley, wall on Station Road by Richard Law
NT2776 : Pivot bench mark, 135 Constitution Street, Leith by Alan Murray-Rust
SW5140 : OS benchmark - St Ives, St Brigid's Apartments by Richard Law
SJ9571 : OS benchmark - Higher Ridgegate, No 1 Clarke Lane by Richard Law
SJ6910 : OS benchmark, Ketley Bank by Richard Law
SP1786 : OS benchmark - Chelmsley Wood, 1 Moorend Avenue by Richard Law
NS4863 : Paisley Abbey: bench mark by Lairich Rig
SN4120 : OS benchmark and 1GL bolt - Carmarthen Guildhall by Richard Law
SK5717 : Bench mark, Baptist Church, Beveridge Street, Barrow upon Soar by Alan Murray-Rust
SP9099 : Bench mark, Seaton Road railway bridge by Alan Murray-Rust
SJ9409 : OS flush bracket - Oak Farm by Richard Law
SP1583 : OS benchmark - Wells Green, 48 Coalway Road by Richard Law
SP1886 : OS benchmark - 129 Chelmsley Road by Richard Law
SJ7008 : OS benchmark - Hollinswood, rear of 133 Dunsheath by Richard Law

... and 2975 more images.

These Shared Descriptions are common to multiple images. For example, you can create a generic description for an object shown in a photo, and reuse the description on all photos of the object. All descriptions are public and shared between contributors, i.e. you can reuse a description created by others, just as they can use yours.
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.

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