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 Due to updated mapping techniques and technological advances such as GPS, bench marks are no longer maintained.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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2545 images use this description. Preview sample shown below:

SK6111 : OS benchmark - Syston, 148 Fosse Way by Richard Law
SJ5301 : OS benchmark - Acton Burnell, St Mary's Church by Richard Law
NO5603 : OS bolt and cutmark - Cellardyke, St Adrian's church by Richard Law
SJ9308 : OS benchmark - Calf Heath, Goldie Brook Bridge by Richard Law
SP1286 : OS benchmark - Yardley Fields, 106/108 Stuarts Road by Richard Law
J3371 : Bench Mark, Belfast by Rossographer
SK8024 : Bench mark, Waltham water tower by Alan Murray-Rust
SK6233 : Rivet bench mark, Normanton bridge by Alan Murray-Rust
SK8271 : Bench mark, North Clifton railway bridge by Alan Murray-Rust
SJ4811 : OS benchmark - Kingsland, wall on Canonbury by Richard Law
SK7724 : Bench mark, railway bridge near Wycomb by Alan Murray-Rust
SD0698 : OS benchmark - railway building at Drigg crossing by Richard Law
SX2051 : OS benchmark - Polperro, wall outside Penlea by Richard Law
J4844 : Bench Mark, Downpatrick by Rossographer
SK5638 : Bench mark, Wilford Bridge by Alan Murray-Rust
SO7188 : Non-OS benchmark - disused gatepost on track by Richard Law
SK5540 : Bench mark, Lenton Boulevard, St Paul's Church by Alan Murray-Rust
TG4719 : OS benchmark - West Somerton by Richard Law
SJ6712 : OS benchmark - Hadley, 26 Hadley Park Road by Richard Law
SP0091 : OS benchmark - West Bromwich, Moor St railway bridge by Richard Law
SP1480 : OS benchmark - Worlds End, 499 Warwick Road by Richard Law
H5180 : OS NI Benchmark by Kenneth  Allen
TR1366 : OS flush bracket - Swalecliffe church hall by Richard Law
SK9218 : Bench Mark, Thistleton Lane bridge by Alan Murray-Rust
NO4102 : OS benchmark - Lower Largo, Drummochy Road by Richard Law

... and 2520 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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