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U.K. and Ireland Trigpoints
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All survey marks or objects used by the UK Ordnance Survey, Ordnance Survey Northern Ireland (OSNI)

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Expanded Description:
All survey marks or objects used by the UK Ordnance Survey, Ordnance Survey Northern Ireland (OSNI) Ordnance Survey Ireland (OSI)& EA Environment Agency. Can include Cut bench marks, Rivets, Flush Brackets, Trig pillars in fact any point used and recorded by ordnance survey, OSNI or OSI. This category can include Triangulation Stations placed by the Admiralty Hydrographic Department that feature on various points around the UK coast. Can also include EABM (Environment Agency Bench Mark). Trigpoints are the common name for "triangulation pillars". These are concrete pillars, about 4' tall, which were used by the Ordnance Survey in order to determine the exact shape of the country. They are generally located on the highest bit of ground in the area, so that there is a direct line of sight from one to the next. By sitting a theodolite (an accurate compass built into a telescope) on the top of the pillar, accurate bearings to nearby trigpoints could be taken.
This category also includes any confirmed other Ordnance Survey marks such as cut bench marks, O/S tide markers, OS rivets, OS bolts, Fundamental bench marks, surface blocks, Berntsen's, blocks, passive and active GPS active stations and flush bracket's on constructions other than trig pillars. Many cut bench marks can be researched on (1890's OS maps) which show their exact location and height. If you know of any other easily accessible resources please let group know.

EABM's are placed by the Environment Agency

Related and other useful sites. (OSGB36)

OS benchmarks (OSGB36) non trig pillar marks

Yahoo trig group Membership needed. Co-ordinate conversion

MSN OSBM group (OSGB36) (variety of datums) Co-ordinate conversions

OS map of Active Stations (OSGB36) uses WGS84 datum. Other sites use other datums.

Here are definitions of common OS marks.
OSBM BOLT "OSBM Bolt" is quite large - an inch or two in diameter (25 - 50mm) (sizes vary), with letters "O S B M" and an arrow engraved into the Bolt itself.(Some of the older ones have no markings.) Bolt
1GL BOLT or PA BOLT1GL BOLT or PA BOLT is a cut mark with a small bolt. The bolt can be next to the cut benchmark or in the apex. 1GL BOLT or PA BOLT
CUT BENCHMARK A cut mark in stone/brick. Some have been found upside-down. CUT BENCHMARK
RIVET WITH CUT BENCHMARK. A rivet is a small round headed bolt no more than half and inch (12mm) in diameter. They are situated ABOVE a cut benchmark. RIVET WITH CUT BENCHMARK
FUNDAMENTAL BENCHMARK. These are about a foot high (30 cm) with a large bolt on top, with a metal plaque. Worth noting also is that some standard FBMs have been cut down to ground level. Some of these have a new bolt on top, but not all. FUNDAMENTAL BENCHMARK
FLUSH BRACKET. These can be found on trig pillars, buildings, bridges etc. They all have an individual number, which you should log. FLUSH BRACKET
SURFACE BLOCK. A rivet set in a concrete base about 6 inches across (15cm) flush at ground level. SURFACE BLOCK
RIVET AND BENCHMARK (OLD STYLE) I have been told that it is the old style of rivet. It is like a headless nail which has been driven into the granite. The top of the stump protrudes out of the rock by about a quarter of an inch (6mm). The only place I have found one is on Dartmoor, where there are several. RIVET AND BENCHMARK (OLD STYLE)
PIVOT BENCH MARKS. A benchmark which has an empty hole above it. There is no horizontal mark. PIVOT BENCH MARKS
PROJECTING BRACKET. These brackets are the predecessor to the Flush Bracket. 258 listed on OSBM. PROJECTING BRACKET
BERNTSEN. Visible is a metal circular lid about 6 inches across (15cm) at ground level, covering a brass bolt. BERNSTEN
CURRY STOOL is a horizontal concrete tripod at ground level with arms about 3 feet (1m) long & a centre stud. 9 known in the UK. CURRY STOOL
BLOCKS. These are similar to a surface block, often replacing (and made from the remains of) a destroyed trig pillar. 17 known in the UK.
WM8CME is one
ACTIVE STATIONS contain a GPS receiver antenna and sometimes meteorological instruments. Active Station Map. (Not publicly listed by OS.) Find an Active Station. Active
CONCRETE RING with a centre stud. 2 feet (55cm) diameter. 6 known in the UK. CONCRETE RING
(The pictures below have been borrowed from T:UK which will be replaced with our own waymarking photos when the objects have been submitted. If you are submitting any of the objects please could you let a manager know.)
FENOMARK. 10 of these are known in the UK. FENOMARK
CENTRE is a small cross engraved in metal. There are 2 known in the UK. CENTRE
GRAVITY FBM. Similar to a standard FBM, but bigger, and with a flush bracket. 4 known in the UK. GRAVITY FBM
BURIED BLOCKS 5 known. Like Surface Blocks but roughly one to two feet underground. (No photos in Waymark database yet.)
SPIDER. There are 6 left in the UK. They are similar to the spider on top of standard trig pillar, but placed elsewhere. e.g. in a wall (No photos in Waymark database yet.)
There are ANOMILIES. A raised block without Flush Bracket but with OSBM bolt under a trap door. Irish Pillar
Other survey marks.
EABM (Environment Agency Bench Mark)EABM (Environment Agency Bench Mark)EABM (Environment Agency Bench Mark)

Instructions for Posting a U.K. and Ireland Trigpoints Waymark:
This category requires a CLOSE-UP photo of the OS object and a photo of the object with the general area taken by the waymarker.

When a trig is waymarked 2 photos are required, the trig and one of the flush bracket.

Most waymarkers submit two photos one close up of the object and one a little further away. The object must be recognizable in the photos.

Please ensure you complete both the short and long descriptions including street names if appropriate, nearest hamlet, village or town and County. (If these are not completed then your submission will be rejected.) Postcode is a bonus.

Ensure all Flush Bracket numbers are entered in the appropriate field.

Instructions for Visiting a Waymark in this Category:
A photo should be taken when you visit, and added to the log.
Category Settings:
  • Waymarks can be added to this category
  • New waymarks of this category are reviewed by the category group prior to being published
  • Category is visible in the directory
  • Type of Trigpoint
  • Condition
  • Number on Flush Bracket
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Image for Cut benchmark and bolt, St Edmund - Southwold, Suffolkview gallery

NWNW158.5 km

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U.K. and Ireland TrigpointsCut benchmark and bolt, St Edmund - Southwold, Suffolk

in U.K. and Ireland Trigpoints

Cut benchmark and PA bolt on south face, south west angle, of church tower.

posted by: Groundspeak Premium Member SMacB

location: Eastern England, United Kingdom

date approved: 6/9/2014

last visited: 9/22/2018

Premium Member Downloads: download.GPX Lite File       download.LOC File       download .KML File (Google Earth)