NY4056 : Flush bracket benchmark, Scotch Street
taken 18 years ago, near to Carlisle, Cumbria, England

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