Bench Marks

Bench Marks are an intriguing feature which are found carved in to the walls of all kinds of buildings and features across the country. Broadly, they form a national network of markers indicating heights above sea level and also indicate relative heights within a locality against each other – each site should be firmly anchored to bedrock.

If you have a bench mark on your property or have spotted one in a public place, please get in touch (see the table, below, for OS grid refs). If you can let us have precise location details and photographs we can add them to our website and improve our records – thank you!

They are defined by Ordnance Survey as:

“Ordnance Survey Bench marks (BMs) are survey marks made by Ordnance Survey to record height above Ordnance Datum. If the exact height of one BM is known, the exact height of the next can be found by measuring the difference in heights, through a process of spirit levelling.

Bench Mark on the outside of the Church
Bench Mark on the outside of the Church

“Most commonly, the BMs are found on buildings or other semi-permanent features. Although the main network is no longer being updated, the record is still in existence and the markers will remain until they are eventually destroyed by redevelopment or erosion.

Bench Mark on the outside of the Church
Bench Mark on the outside of the Church

“Bench marks are the visible manifestation of Ordnance Datum Newlyn (ODN), which is the national height system for mainland Great Britain and forms the reference frame for heights above mean sea level. ODN is realised on the ground by a network of approximately 190 fundamental bench marks (FBMs). From these FBMs tens of thousands of lower-order BMs were established. The network has had little maintenance for 30 years, and in some areas (mining areas for example), subsidence has affected the levelling values. In these regions the BMs cannot be relied upon to accurately define ODN.

“There are approximately 500 000 ‘lower order’ BMs still remaining. This number is reducing due to property development, road widening and so on. The BM heights shown have not been maintained for 30 years and should not be relied upon to accurately define ODN.

“There are approximately 190 FBMs, which as the name suggests are our high-accuracy BMs. These are still maintained and are still used by Ordnance Survey. They form our primary height network and, as such, are our link to the Ordnance Datum at Newlyn. They are used in the creation of the orthometric to GPS height correction model (OSTN15). The FBMs are not available through this website. Access to FBM values will be considered on a case by case basis on application to Ordnance Survey.”

https://www.ordnancesurvey.co.uk/benchmarks/

St. Luke’s Parish Church:

Bench Mark on the outside of the Church
Bench Mark on the outside of the Church
Bench Mark on the outside of the Church
Bench Mark on the outside of the Church
Sun Dial on the wall of the Church
Sun Dial on the wall of the Church

Sycamore Lodge:


Benchmark on the wall of Sycamore Lodge, Green Lane

Benchmark on the wall of Sycamore Lodge, Green Lane

Stone Trough, Spring, north of Green Lane:

Wadkin Archive; W0890a

Wadkin Archive; W0890b
Wadkin Archive; W0890aa

Wadkin Archive; W0890bb

NG LETTERSEASTINGNORTHINGHEIGHTTYPE OF MARKHEIGHT ABOVE GROUNDVERIFIED DATEDESCRIPTIONParish:OS line ref:   
SK6835262389.0168 0.71962ST LUKES CH S FACE 3.4M SE ANG U Broughton348994
SK6873260967.181 0.81962BLDG S SIDE MELTON RD W FACE NW ANG N Broughton348995
SK6802277073.2191 0.21962NBM SPRING SURROUND S ANG Hickling/Green Lane348996
SK6803275581.1317 0.31962NBM FM BLDG C SW FACE SE SIDE GREEN LANEHickling/Green Lane348997
SK6809287255.754RIVET 01962NBM RIVET CUL N SIDE BRIDEGATE LANE ENT BARLAND FIELDS Hickling/Bridegate348998
SK68322824105.025FL BR 01962FL BR S4637 HICKLING STANDARD Trig Point Hickling348999
SK6862288449.3197 0.31962GTP N SIDE BRIDEGATE LANE 39.6M SW HEDGE JUNC Hickling/Bridegate349000
SK6893284756.4977 0.61962NBM FM BLDG SW ANG NW SIDE PATH Hickling/fields349001
SK6812310442.255FL BR 0.21957FL BR 10070 NE FACE N ANG OULTON GRANGE SW SIDE OWTHORPE LANEKinoulton349002
SK6814310342.1282 0.61957N ANG PH NEVILE ARMS OWTHORPE LANEKinoulton349003
*Flush Bracket
*Rivet - literally a metal rivet, sometimes with the 3 descending/fan lines seen on a benchmark
SK6959261480.1228 0.81962BARN NW SIDE RD C SE FACE N Broughton349179
SK6918276950.1396 0.71962BR DALBY BROOK NE PARA NW END Hickling/NBr349180
SK6902289645.9395 0.71962WOLD COTTAGE N SIDE BRIDEGATE LANE SE ANG S FACEHickling349181
SK6909289945.2384RIVET 0.61962NBM RIVET ROCK NE ANG HICKLING METH CH WALL Hickling349182
SK6911288847.3964 0.61962BLDG W SIDE MAIN ST OPP MARCHS FM HO SE ANG E FACE Hickling349183
SK6913285849.0484 0.41962NBM HO S SIDE LONG LANE N FACE 13.4M NE ANG Hickling349184
SK6914282651.1272 0.51962GTP 29.0M N HEDGE JUNC E SIDE MAIN ST Hickling349185
SK6954289446.7746 0.41962GTP N SIDE CLAWSON LANE 9.8M NE HEDGE JUNC Hickling349186
SK6917292745.7291 11962ST LUKES CH TWR SW ANG Hickling349187
SK6918299940.8127RIVET 0.51962NBM RIVET CUL DALBY BROOK N PARA W END Hickling349188
SK6987299942.0319RIVET 01962NBM RIVET CATTLE GRID N SIDE RD HEDGE JUNC Hickling349189
SK6955306339.1638RIVET 0.21962NBM RIVET CONCRETE BASE PYLON E ANG Hickling349190
SK6972303240.2458RIVET 0.31962NBM RIVET CONCRETE BASE PYLON W ANG Hickling349191
SK6968318035.2379RIVET 01962NBM RIVET CONCRETE BASE PYLON E SIDE PATH E ANG Kinoulton349192
SK6969316634.4272RIVET 01962NBM RIVET FB S END W SIDE PATH Kinoulton349193
SK6939325533.1409RIVET 0.21962NBM RIVET SE PARA BR R SMITEKinoulton349194
SK6945323933.4091RIVET 01962NBM RIVET E PARA BR R SMITE Kinoulton349195
SK6971329636.8686 0.51962WALL E SIDE SCHOOL LANE 18.3M S ANGEL COTT Colston Bassett349196
SK71042425105.5614 0.51962GTP NE SIDE NOTTINGHAM RD 15.2M SE PRODN HEDGE JUNC N Broughton349617
SK7183269675.5203 0.51962BARN N SIDE RD JUNC C S FACEL Clawson349618
SK7189266979.5924 0.81962NO1 BAYLIS COTTAGES MELTON RD E FACE NE ANG L Clawson349619
SK7177270572.8503 0.31962NBM CONCRETE SNP NE SIDE HICKLING LANE SW FACE L Clawson349620
SK7101282359.3872 0.61962OUTBLDG CASTLE VIEW FM SW SIDE RD 0.9M E ANG NE FACEHickling? 1*349621
SK7108285052.261 0.71962NBM BLDG FEALER FARM W ANG SW FACE Hickling? 1*349622
SK7185288051.7185 0.51962GTP HEDGE JUNC Hickling? 1*349623
SK7107292145.6164RIVET 0.81962NBM RIVET SWING BRIDGE S PARA SE ANGHickling? 2*349624
SK7150294042.7665RIVET 0.81962NBM RIVET CUL NE SIDE STR Hickling? 2*349625
SK7174297045.2415RIVET 0.41962NBM RIVET BR S PARA SW END Hickling? 2*349626
SK7152306851.4868 0.61962NBM COLSTONHILLS FM HO N ANG NW FACEHose349627
1* fields between LC & Hickling
2* canal between Hose & Hickling
OS grid references for benchmarks & trig point
OS grid references for benchmarks & trig point

There are some really useful websites that are supporting research in to remaining bench marks:

An Ordnance Survey Blog: Keeping our fundamental bench marks in order:

Lampeter FBM blog image

“Most people are familiar with trig pillars. There are over 7,000 of them scattered around Great Britain. However, there is another, considerably more elusive, type of pillar to be seen across the land – the fundamental bench mark (FBM). FBMs are the physical realisation of our national height datum ‘Ordnance Datum Newlyn’ (ODN – mean sea level at Newlyn, Cornwall, 1915-1921) and are still crucial in defining this reference system today.

“There are nearly 200 FBMs around Great Britain, mostly constructed in the first half of the twentieth century at sites carefully selected to provide an anchor to bedrock. The height of each FBM relative to ODN was determined by a network of precise levelling lines across the country. The levelling network was then densified with approximately three-quarters of a million bench marks, using less precise levelling. These lower-order bench marks are often seen cut into stone at the base of a building, church or bridge and about half a million of them are still in existence today.”

(For Hickling, there is a trig point on the top of the Hickling Standards)

Benchmark or trig pillar: what’s in a name?

An illustrated Ordnance Survey article detailing the differences between benchmarks, fundamental benchmarks, flush brackets and trig points: click the title, above, to read this.


https://www.bench-marks.org.uk/viewsearch?q=fe9730060bb00925b7289498feb8e58e

bench-marks.org search results 09.2019 (unfortunately, no key to symbols available)
https://www.bench-marks.org.uk/flush

Wikipedia entry:

The term benchmark, or bench mark, originates from the chiseled horizontal marks that surveyors made in stone structures, into which an angle-iron could be placed to form a “bench” for a leveling rod, thus ensuring that a leveling rod could be accurately repositioned in the same place in the future. These marks were usually indicated with a chiseled arrow below the horizontal line.

The term is generally applied to any item used to mark a point as an elevation reference. Frequently, bronze or aluminum disks are set in stone or concrete, or on rods driven deeply into the earth to provide a stable elevation point. If an elevation is marked on a map, but there is no physical mark on the ground, it is a spot height.

The height of a benchmark is calculated relative to the heights of nearby benchmarks in a network extending from a fundamental benchmark. A fundamental benchmark is a point with a precisely known relationship to the vertical datum of the area, typically mean sea level. The position and height of each benchmark is shown on large-scale maps.