Ordnance Survey Benchmark. Prior to 1875. King Edward's Parade, Eastbourne. what3words location: cheek.took.ritual

A combined War Department Boundary Stone and Benchmark (plus Bath Chair Stand Licence Plate).

Boundary wall of the Wish Tower opposite the Lansdowne Hotel near entrance to Western Lawns. 

From OS: The horizontal marks are used to support a stable ‘bench’ for a levelling stave to rest on – hence ‘benchmarks.’  Used to ‘record height above ordnance datum’ for mapping purposes.  Although no longer used (OS now use GPS), the records still exist and the markers will remain until they are eventually destroyed by redevelopment or erosion.

Historic Context:  Ordnance Survey has its roots in military strategy due to the mapping of the Scottish Highlands following a rebellion in 1745.  Later, during the French Revolution there were fears the bloodshed might sweep across to our shores.  The government ordered its defence ministry of the time – the Board of Ordnance – to begin a survey of England’s vulnerable southern coasts.  Until then, maps had lacked the detail required for moving troops and planning campaigns.  The date of 21 June 1791 is officially recognised as the birth of Ordnance Survey. The term ‘Ordnance Survey’ was not used at all until 1801 when its director wrote it on a draft document. The name was not printed on a map until the 1810 ‘Ordnance Survey of the Isle of Wight and part of Hampshire”.  In the mid-1830s, height was introduced to Ordnance Survey maps (this is where benchmarks come into the picture).  In 1841, the Survey Act gave surveyors a legal right to ‘enter into and upon any land… for the purposes of making and carrying out a survey’.  In 1983 the last military personnel left Ordnance Survey, making it a wholly civilian organisation.  The War Department’s broad arrow remained in the Ordnance Survey Logo a further 21 years afterward, a nod to its military past.

References: -

Ordnance Survey website for OS history and benchmark information.