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 Due to updated mapping techniques and technological advances such as GPS, bench marks are no longer maintained.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
Related descriptions Selection is automatic and approximate, it might not always select closely matching descriptions

1973 images use this description. Preview sample shown below:

J3272 : Bench Mark, Belfast by Rossographer
SJ7010 : OS benchmark - Snedshill, no 1 Furnace Lane by Richard Law
SJ7200 : OS benchmark - Norton, the old school by Richard Law
SJ7512 : OS benchmark & bolt - Sheriffhales church by Richard Law
SP1189 : OS benchmark - Ward End, 26 Ingleton Road by Richard Law
C8532 : Bench Mark, Coleraine by Rossographer
SJ8890 : Bench mark and bolt, Georges Road bridge by Alan Murray-Rust
SK9303 : Bench mark, Sunny Knoll, Digby Avenue by Alan Murray-Rust
J3575 : Bench Mark, Belfast by Rossographer
SP1584 : OS benchmark - Sheldon, 95 Whitecroft Road by Richard Law
J5281 : Bench Mark, Bangor by Rossographer
SK7953 : Bench mark, Town Hall  by Alan Murray-Rust
SO6596 : OS benchmark - Hawthorne Farm barn by Richard Law
SK7390 : Bench mark and bolt, Gringley Church by Alan Murray-Rust
SK5337 : Rivet bench mark alongside Queens Road by Alan Murray-Rust
SJ9607 : OS benchmark - Cheslyn Hay, gatepost on Saredon Road by Richard Law
J3377 : Flush Bracket, Belfast by Rossographer
SJ6703 : OS benchmark - Ironbridge, Madeley Road by Richard Law
SJ8712 : Remains of OS rivet, All Saints Church by Richard Law
ST8042 : Bench Mark, Longleat by Rossographer
SK7080 : Bench mark, Icon Polymers, Thrumpton Lane by Alan Murray-Rust
SK7851 : Bench mark, Devon Bridge, Hawton by Alan Murray-Rust
SK9214 : Bench Mark, 16 Great Lane by Alan Murray-Rust
SJ7420 : OS benchmark, Chetwynd Road by Park Pool by Richard Law
SK8907 : Bench mark, Hilltop, Hambleton by Alan Murray-Rust

... and 1948 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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