Concrete Ring

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The original exposed Concrete Ring at Blencathra
The replacement Concrete Ring at Blencathra
A buried Concrete Ring
Example of inscription

'Concrete Ring' is a trig bagger's term denoting a feature of some buried blocks seen in Lakes/Northern Pennines and elsewhere. Typically, the ring is approx 15" internal and 21" external diameter. It usually bears the inscription "Ordnance Survey Trigonometrical Station" although this may be eroded or absent. The ring is placed loosely above the block. The block itself typically has a central, slightly conical bolt of approx 3" diameter. Occasionally, a ring may be used to mark a buried bolt set into bedrock, for example, Brownsey Moor. Infrequently, the trig mark may be a rod instead of a bolt, for example, Stonesdale Moor.

Initially, when very few examples of concrete rings had been found, they were considered by some baggers to be a decorative feature, lacking a functional use. Subsequently, it was understood that they were identical to the OS term Emplacement Ring (or Detector Ring) as described in Section 7.032 and Fig 7.7 of The History of the Retriangulation of Great Britain [1] as follows: When used as a secondary station a phosphor-bronze ring was buried with the block so as to enable it to be detected by mine detectors if the locating description should prove insufficient. With the lower order stations these rings were replaced by scrap iron incorporated in the block itself.

Some, but not all, concrete rings have an embedded metal ring (originally phosphor-bronze, subsequently iron). As with detector plates, the ring can assist in locating a trig when using a metal detector but is not in itself a mark.

It was discovered quite late on that the manufacturer decided to leave out the metal ring to save money. Hence many rings are just concrete [2].

The OS online records do not identify which blocks have emplacement rings, hence it is not known how many exist. The paper-based OS Office files (held at The National Archives) and Field files are understood to record this information although not systematically [3].

Until 2014, 10 Concrete Rings had been located, all in Northern England. However, they have subsequently been located more widely with 26 having been identified by late 2019, 51 by the end of 2022 and 55 by the end of 2023.

A photo album of concrete rings is available from T:UK, where a listing can also be accessed.

In 2018 the Concrete Ring on the buried block at Saddleback, located at the summit of Blencathra, was reported missing, presumed stolen. A replica was installed in early 2019 and has since suffered minor damage. The ring for Moss Farm was also lost, a few months after its rediscovery.

Trig Stations with a Concrete Ring
T:UK Station name Order Computed Block Date found Finder
TP19379 Abercwmboi Auxiliary 4 1953 SO11 2 Jun 2019 Dusty
TP15266 Ben Barvas 2 1956 NC20 17 May 2022 peregrinus
TP16849 Biggin Farm 4 1957 NZ42 28 Mar 2021 CJO
TP17382 Bleak Hill 4 1954 SE22 22 Nov 2021 Mickandkim
TP20335 Brith-Weunydd 4 1953 ST07 26 May 2019 Dusty
TP8086 Brownsey Moor 3 1955 SE38 8 Oct 2022 CJO
TP19356 Bryn Du 4 1953 SO11 20 Jul 2018 Dusty
TP23704 Burchetts Green 4 1952 TQ08 24 May 2015 Berries
TP17465 Busk Moss 3 1955 SE38 16 Aug 2020 CJO
TP19359 Craig-Y-Gilfach 4 1953 SO11 3 Jun 2018 Dusty
TP19387 Cwmaman 4 1953 SO11 23 May 2022 Dusty
TP25851 Cwmaman Auxiliary 4 1953 SO11 23 May 2022 Dusty
TP17471 Easterside Hill 3 1955 SE38 21 May 2022 CJO
TP19360 Ffos-Y-Fran Reservoir 4 1953 SO11 8 Jun 2019 Dusty
TP21679 Four Burrows 4 1955 SX07 16 Apr 2022 peregrinus
TP00057 Gallow Hill 3 1952 NS29 23 Apr 2022 peregrinus
TP20383 Graig Fach 4 1953 ST07 6 Sep 2014 Dusty
TP19213 Graig Fawr 4 1953 SO11 21 Jul 2019 Dusty
TP17473 Great Haw 3 1955 SE38 24 Feb 2019 CJO
TP7367 Great Yarlside 3 1961 NY71 30 Jul 1988 peregrinus
TP17474 Greets Hill 3 1955 SE38 9 Jan 2022 CJO
TP20397 Gwaelod-Y-Garth 4 1954 ST07 28 Oct 2019 Dusty
TP17476 Harland Hill 3 1955 SE38 9 Mar 2019 CJO
TP16529 High Banks 2 1953 NY45 29 Jan 2023 CJO
TP7507 High Seat 3 1962 NY71 23 Sep 2008 Phil Clayton
TP17478 Ivy Scar 3 1955 SE38 3 Oct 2022 peregrinus
TP17479 Jingle Pot 3 1955 SE38 21 Nov 2021 CJO
TP17484 Knavy Knot 3 1955 SE38 15 Jan 2023 CJO
TP7379 Knipe Moor 3 1961 NY71 4 Mar 1990 lonesome_cowboy_burt
TP17274 Ladysmith Camp 4 1952 SD80 25 Oct 2022 Mickandkim
TP17480 Lodge Pasture 3 1955 SE38 21 Apr 2019 CJO
TP23701 Maidenhead Thicket 4 1952 TQ08 12 Apr 2015 Berries
TP17273 May Hill 4 1952 SD80 5 Nov 2022 peregrinus
TP17123 Middle Dale 3 1950 SD47 6 Feb 2020 Dusty
TP17342 Middle Healey 4 1949 SE02 3 Aug 2020 Murky
TP16545 Millstone Rigg 4 1962 NY71 5 Sep 2017 jonglew and RogerTempleman
TP17336 Moss Farm 4 1949 SE02 3 Mar 2021 Mickandkim
TP25794 Mynydd Aberdar Auxiliary 4 1953 SO11 5 Jun 2019 Dusty
TP19345 North Merthyr Quarry 4 1953 SO11 7 Jul 2018 Dusty
TP20230 Polmenna 3 1949 SS30 17 Apr 2022 peregrinus
TP7306 Saddleback 3 1953 NY45 8 Apr 1977 arranc
TP7493 Sails 3 1962 NY71 30 Jul 1978 Clayton
TP7368 Seat Robert 3 1961 NY71 4 Mar 1990 lonesome_cowboy_burt
TP7307 Selside Brow 3 1961 NY71 5 Jun 1991 PhilPamAndRob
TP8083 Shaw 3 1955 SE38 17 Sep 2022 CJO
TP17275 Slatepit Moor 4 1952 SD80 25 Oct 2022 Mickandkim
TP7380 Stonesdale Moor 3 1962 NY71 9 Aug 2005 Michael Fisher
TP17343 Stormer Hill 4 1949 SE02 15 May 2019 ted
TP7506 Swarth Fell Pike 3 1962 NY71 19 Dec 1998 dugswell2
TP7818 Tees Head 3 1962 NY71 20 Aug 2011 ted
TP19362 Twyn Croes 4 1953 SO11 3 Aug 2018 Dusty
TP17453 Virgin Moss 3 1955 SE38 23 Feb 2019 CJO
TP17454 Wasset Fell 4 1955 SE38 22 Aug 2020 CJO
TP8362 Heughscar Hill 3 1961 NY11 28 Aug 2023 CJO
TP20307 Hillsborough 3 1949 SS72 20 Dec 2023 CJO
TP16817 Danesly Hill 3 1954 NZ42 3 Feb 2024 CJO
TP17475 Grimbald Crag 3 1955 SE38 11 Feb 2024 CJO
TP21394 Pyle Hill 3 1954 SU77 11 Feb 2024 peregrinus
TP16826 Warren House 4 1954 NZ42 15 Jun 2024 CJO
TP19374 Plas-Y-Coed 4 1953 SO11 21 Jun 2024 Dusty, peregrinus

Since the number of rings emplaced is not known these stats may be not be based on a representative sample.

Trig Stations where a Concrete Ring is suspected but not confirmed
T:UK Station name Order Computed Block Notes
TP755 Bolnhurst 2 1938 TL36 Passive station sketch T1TL0559 refers to "B/B with Detector R"
TP17351 Denehurst Farm 4 1953 SE02 Sketch.

Document in Office file states "Detector Ring inserted". Station thought to be destroyed (land slip).

TP18663 Linthwaite 4 1954 SK39 Sketch 1 and

2. The Reconnaissance Report mentions Detector Ring

TP17488 Snilesworth Moor 3 1955 SE38 Sketch.

The Reconnaissance report mentions 'Det Ring' and the Maintenance report states "Detector Material Situate: Yes Detector Ring"

TP16497 Watch Hill 3 1952 NY11 The Office File states "Detector Ring in place" but when found in Aug 2023 a Detector Plate was identified.
TP16498 Aikbank 3 1952 NY11 Station Inspectors Report "Buried Block Detector Ring"
TP16502 Monkwray Brow 3 1952 NY11 "Detector Ring in situ"
TP16504 Redness 3 1952 NY11 "Detector Ring"
TP23536 Church Hill 4 1951 TQ00

Pillar Constructors Report "Detector Ring was placed", "Depth of top of block 24 inches"

TP18950 The Nurseries 4 1950 SK73 Sketch. Document in Office file states "Detector Ring".

Housing on site; station probably destroyed.

TP16505 Bankend 3 1952 NY11 "B/Block 1'6" Below G.L with Detector Ring"
TP16539 St Anns Hill 3 1953 NY45 "Detector material situate Yes" (nature of material not specified)
TP21316 Windmill Hill 3 1951 SU59

"Detector Ring"


References

  1. The History of the Retriangulation of Great Britain 1935-1962, p.226
  2. email from Ian Wilson to the Trigonomy mailing list, 15 July 2009
  3. Email from Ian Wilson to the Trigonomy mailing list, 25 September 2013