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 Due to updated mapping techniques and technological advances such as GPS, bench marks are no longer maintained.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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1292 images use this description. Preview sample shown below:

SO9395 : OS benchmark - Ladymoor, canal bridge by Richard Law
SP1482 : OS benchmark - Olton, 26 Moordown Avenue by Richard Law
SK3830 : Bench Mark on Chellaston church by Alan Murray-Rust
SJ5501 : OS rivet & cutmark, Bullhill Brook bridge by Richard Law
C4416 : Bench Mark 3339, Derry / Londonderry by Kenneth  Allen
SJ9708 : OS benchmark - Bridgtown, culvert over stream by Richard Law
SO7192 : OS benchmark - Bridgnorth, 15 Railway Street by Richard Law
SK7267 : Flush bracket bench mark, Old Bar Farm, Laxton by Alan Murray-Rust
SK5434 : Bench mark, St Mary's Church, Clifton by Alan Murray-Rust
J4179 : Flush Bracket, Holywood by Rossographer
SO7293 : OS benchmark - Bridgnorth, Hermitage Hill wall by Richard Law
SK7640 : Bench mark, Elton and Orston Station bridge by Alan Murray-Rust
SK8871 : Bench mark on Harby Station bridge by Alan Murray-Rust
SJ9901 : OS benchmark - no 107 Somerfield Road by Richard Law
SO4594 : OS benchmark - Church Stretton, Burway Road by Richard Law
D1241 : Bench Mark, Ballycastle by Rossographer
SK6587 : Bench mark, St Barnabas Church, Ranskill by Alan Murray-Rust
SO7193 : OS benchmark, Bridgnorth, 25 Salop Street by Richard Law
SJ5302 : OS benchmark - Acton Burnell, Rural Cottages by Richard Law
SK5238 : Bench mark, Lenton Abbey Park Lodge by Alan Murray-Rust
SK6876 : Bench mark, Jockey House milestone by Alan Murray-Rust
SJ6604 : OS benchmark - Coalbrookdale, bridge east of Darby Road by Richard Law
SO7193 : OS benchmark - Bridgnorth, on 50 Friars Street by Richard Law
SP1484 : OS benchmark - Lyndon End, 1990 Coventry Road by Richard Law
SK4637 : Bench mark, School Lane by Alan Murray-Rust

... and 1267 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: Wed, 8 Jun 2011

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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