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 Due to updated mapping techniques and technological advances such as GPS, bench marks are no longer maintained.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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1617 images use this description. Preview sample shown below:

SP1183 : OS flush bracket, Acock's Green infants school by Richard Law
SJ5015 : OS benchmark - Shrewsbury, no 13 Morville Road by Richard Law
SK5539 : Bench mark, Harrington Drive by Alan Murray-Rust
SK7660 : Rivet bench mark, Bathleyford Bridge by Alan Murray-Rust
SJ9900 : OS benchmark - no 119 Bloxwich Lane by Richard Law
SJ5504 : OS benchmark - Cound, St Peter's church by Richard Law
SJ5401 : OS benchmark - Sham Castle entranceway by Richard Law
SK7768 : Bench mark, Church of All Saints, Weston by Alan Murray-Rust
TF2643 : Bench mark, Hubbert's Bridge Farm by Alan Murray-Rust
SK5539 : Bench mark, Park keeper's lodge, Lenton Recreation Ground by Alan Murray-Rust
NO3801 : OS flush bracket S4215 - Leven trig point by Richard Law
SD1482 : OS benchmark - lane south of Whicham Hall by Richard Law
SK5336 : Bench mark, #132 Queens Road, Beeston by Alan Murray-Rust
SU9677 : Flush Bracket, Windsor by Rossographer
J4582 : Bench Mark, Helen's Bay by Rossographer
SH5800 : OS Flush Bracket S0342 - Tywyn, St Cadfan's church by Richard Law
SP1588 : OS benchmark - Shard End, Flat 256 Packington Avenue by Richard Law
NO4209 : OS rivet - bridge south of Gathercauld by Richard Law
SJ6410 : OS benchmark - Wellington, Ercall Lane by Richard Law
SJ7419 : OS benchmark - Newport, no 54 High St by Richard Law
C6322 : South Base Station, Lough Foyle Base Line by Rossographer
SO9098 : OS benchmark - 96 Lord Street by Richard Law
H9639 : Flush Bracket, Markethill by Rossographer
SO2296 : OS benchmark - Montgomery, Kerry Road junction by Richard Law
SK7054 : Normanton Hall by Alan Murray-Rust

... and 1592 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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