SecretLeeds - History, culture and architecture in Leeds

I took this photo on January 11 2012. I shows a close-up view of a possibly very old Bench Mark (BM) on a stone pillar at the side of Bartles Lane (the track that goes from Arthington Road to the A660 Otley Road) shortly before reaching the entry gate into Golden Acre Park (coming from Arthington Road). The BM is not at all readily spotted. What may be more interesting about this BM is that it is not recorded on maps I've seen in the Old-Maps UK website, namely those from 1893 to at least 1965. Those maps do however record a BM that is just through the nearby entry to Golden Acre Park. It seems to be a secret BM of Leeds (well it does to me! ).I shall post a wider field-of-view next to show where the BM can be seen.

This photo shows the location of the Bench Mark, which is on the pillar on the left (the pillars were likely once the posts for a gate).

Possibly a re-used stone, Leodian. I don't think bench marks were carved onto stones which could be considered "movable" for obvious reasons. This stone may have been built into a (at the time) more permanent structure, which has since been demolished.

Excuse my ignorance but what were bench marks used for?

It's a reference point for surveyors measuring distance and height.

Cardiarms wrote: It's a reference point for surveyors measuring distance and height. Usually a point measured above mean sea-level (or below if you live in Cambridgeshire.) Their locations can be seen on old maps, as here.Edit: Chrism explains below.     

The term bench mark, or benchmark, 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, brass or aluminum disks are set in stone or concrete, or on rods driven deeply into the earth to provide a stable elevation point.The height of a benchmark is calculated relative to the heights of nearby benchmarks in a network extending from a fundamental benchmark, a point with a precisely known relationship to the level datum of the area, typically mean sea level. The position and height of each benchmark is shown on large-scale maps.The terms "height" and "elevation" are often used interchangeably, but in many jurisdictions they have specific meanings; "height" commonly refers to a local or relative difference in the vertical (such as the height of a building), whereas "elevation" refers to the difference from a nominated reference surface (such as sea-level, or a mathematical/geodetic model that approximates the sea level known as the geoid). Elevation may be specified as normal height (above a reference ellipsoid), orthometric height, or dynamic height which have slightly different definitions.Clear?

This map image was taken from the 1893 1:2,500 map in the Old-Maps UK website. It shows a BM (a small arrow locates it) that is still there today on a pillar just inside Golden Acre Park from the Bartles Lane access. The unrecorded BM can be seen on the right of that lane (when coming from Arthington Road) shortly before reaching the access into the park.I agree with what Si has said in that the stone with the unrecorded BM is "Possibly a re-used stone".    

Some bench marks do seem to be missing from the maps, however. There's one clearly carved into the stone front door surround of what was once the Yeoman pub in Otley, but it's not on the 1906 Godfrey OS map.

Chrism wrote: The term bench mark etc...Clear? (sorry no wish to hijack thread but on chrism's informative note, I've always wondered how so long ago they got such accurate levels.Case point. Eccup>Blackmoor tunnel>7 Arches>From here they built a conduit to take the water on land contour thence Weetwood Aqueduct through the Hollies to Weetwood Resvr. Canals etc too.Stood in the Meanwood beck in the Hollies you have 1. the beck. Then cut into the hill a dam +2. mill race. Then higher still 'the path'/course of 3. conduit.Same with mill race/goits etc. Important to get it right. Leo's thread spot on this as the bench mark would/may have been used for levels for Adel Dam for the mill and later Blackhill Dam (now Golden Acre).So did they use a large number of accurately 'altituded' bench marks, then measure (pre-laser) down/up from these?I defer to your amazing knowledge of things benchmark chrism)