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 Due to updated mapping techniques and technological advances such as GPS, bench marks are no longer maintained.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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2128 images use this description. Preview sample shown below:

SP1976 : OS benchmark - Knowle, Bottom Lock Cottage by Richard Law
SP1688 : OS benchmark - Kingshurst, 418 Chester Road by Richard Law
J2627 : Bench Mark, Spelga Dam by Rossographer
SP1480 : OS benchmark - Worlds End, Greswold Primary School by Richard Law
SK8608 : Bench mark, Market Street, Oakham by Alan Murray-Rust
SK9508 : Bench mark, 71 Main Street, Empingham by Alan Murray-Rust
SJ6919 : OS flush bracket - Tibberton Trig by Richard Law
SP1482 : OS benchmark - Olton, Hob's Meadow pub by Richard Law
C6733 : Flush Bracket, Magilligan by Rossographer
SH7401 : OS benchmark - Heol y Ddol railway bridge by Richard Law
SP2481 : OS benchmark - Meriden, 2 Stone Cottages by Richard Law
SO7193 : OS benchmark - Bridgnorth, no 66 Cartway by Richard Law
SO4593 : OS benchmark - Church Stretton, 42 Essex Road by Richard Law
SP2080 : OS benchmark - Marsh Lane, Hampton in Arden by Richard Law
SJ5204 : OS benchmark - Pitchford Hall, St Michaels church by Richard Law
NS3478 : Bench mark, Darleith Road by Lairich Rig
SP1886 : OS benchmark - no 1 Ludlow Close by Richard Law
TG4620 : OS Flush Bracket - West Somerton by Richard Law
SP1480 : OS benchmark - Worlds End, 133 Buryfield Road by Richard Law
NO5603 : OS benchmark - Cellardyke, former Independent Chapel on Crail Road by Richard Law
SK2422 : OS benchmark - Burton-on-Trent, 178 High Street by Richard Law
SK4637 : The corner of School Lane by Alan Murray-Rust
J5081 : Bench Mark, Bangor by Rossographer
SJ9915 : OS rivet & benchmark, Brindley Road by Richard Law
SJ8102 : OS benchmark - Boningale, St Chad's church by Richard Law

... and 2103 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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