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 Due to updated mapping techniques and technological advances such as GPS, bench marks are no longer maintained.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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2730 images use this description. Preview sample shown below:

SJ6511 : OS benchmark - Wellington New College by Richard Law
J5849 : Flush Bracket, Strangford by Rossographer
SP9197 : Bench mark, Harringworth Viaduct by Alan Murray-Rust
SK7390 : Bench mark, Mill House, Gringley by Alan Murray-Rust
SP1886 : OS benchmark - 118 Coleshill Heath Road by Richard Law
SW3626 : OS benchmark - Sennen school by Richard Law
SJ5012 : Forgotten OS benchmark - Shirehall, south side of Abbey Foregate by Richard Law
SX2553 : OS benchmark - Looe, Watchtower Studio at Church End by Richard Law
NO5016 : OS benchmark - St Andrews, 9 Golf Place by Richard Law
SP1482 : OS benchmark - Ulverley Green, 46 Highwood Avenue by Richard Law
SK6110 : OS rivet - Thurmaston, footbridge support by Richard Law
SK5337 : Bench mark, Sycamore Court by Alan Murray-Rust
SK8053 : Bench mark, 14 Appletongate by Alan Murray-Rust
C9703 : Flush Bracket, Portglenone by Rossographer
NO3700 : OS benchmark - Aberhill, bridge over former railway by Richard Law
SP2388 : OS benchmark, no1 Coleshill Road by Richard Law
J3373 : Bench Mark, Belfast by Rossographer
SP0687 : OS benchmark - Old Snow Hill, Clive Passage by Richard Law
SK7775 : Bench mark, Manor farm, East Drayton by Alan Murray-Rust
SK7079 : Bench Mark, Church of All Hallows, Ordsall by Alan Murray-Rust
SK7734 : Bench mark, St Peter and St Paul Church, Barkestone-le-Vale by Alan Murray-Rust
SP0190 : OS benchmark - West Bromwich, Beeches Road by Richard Law
SM8813 : OS benchmark - Creampots by Richard Law
J5979 : Bench Mark, Donaghadee by Rossographer
SJ7008 : OS benchmark - Hollinswood, no 65 Duffryn by Richard Law

... and 2705 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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