My colleague John Moore pointed out a couple of cut mark Ordnance Survey benchmarks on and around Oxford Road. This prompted me to look up the nearest benchmarks and find them. I’ll keep updating this post as I photograph them – some are currently off-limits because of building work, others have likely been destroyed. These marks are a legacy of a need for marks for local surveyors using optical levels, alidades, chains and plane tables – these marks are no longer maintained by the Ordnance Survey. A modern surveyor will use a GPS receiver that uses a correction signal from a receiver located on a known position – the organisation provides an “active” network of continuously running transceivers on known positions, and a “passive” network of survey marks with published positions upon which a surveyor may locate their own transceiver.
- SJ84849678, Number 81 Upper Brook Street, north-west face, west angle. 38.868m O.D. – No longer extant.
- SJ84579662, Museum, west side Oxford Road, south side gateway, north-east face, north angle. 38.384m O.D. Obscured by building works at present.