EHL61. Ordnance Survey Benchmark 1879-1898. Peregrine House, 29 Compton Place Road, Eastbourne. what3words location: pile.stamp.stars

Left hand gatepost of vehicle entrance to property, 0.6 metres from ground level.  I have superimposed a close-up of the Benchmark onto the main picture.

Between 1879 to 1898.  The ‘BM’ (Benchmark) does not appear on the 1879 map (surveyed 1875 to 1876), but does appear on the revised 1898 map published in 1900.  Last verified in 1970 according to OS website.

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.

Eastbourne maps via National Library of Scotland website: -

OS Six-inch England and Wales, 1842-1952, Sussex Sheet LXXX