This is not the first project to put Ordnance Survey benchmarks on a map. OS runs its own national benchmark viewer, a free app called TrigFindAR already lets walkers tick off marks as found from a phone, and a community of "benchmark baggers" has quietly pursued this hobby for years. A recent project in County Limerick, Ireland, sent volunteers into the field with a mobile survey tool to record one county's benchmarks as found or lost. None of that is claimed here as new.

What this project set out to show instead is what a single person, working alone with no institutional funding, no GIS training and no team, can now build using freely available tools. An AI was used to sort and align the complete national benchmark archive, over half a million records, onto the boundaries of the thirteen historic counties of Wales. The same marks were then split, county by county, into ten interactive layers each: three preserving the levelling network as the Ordnance Survey built it, and seven reading the same marks as local heritage, churches and chapels, farms, bridges and railways, milk stands, wayside features, village landmarks, and upland and living rock. Thirteen live maps and a companion volume for each county followed, bound together by QR codes and tinyurl links so that a printed page leads straight back to the relevant live map with a single scan of a phone.

The result, 43,511 benchmarks recorded across every historic county of Wales, with a full written history, county-by-county narrative, and closing data ledger, was built in a matter of days. Every mark is presently recorded as unvisited, and the invitation behind the whole series is for walkers, schools and local history societies to take their own parish and begin turning that word into a record of what survives. If this project has anything genuinely new to offer the heritage world, it is not the idea of mapping benchmarks, but proof of how far simple, accessible technology can now carry that idea, in the hands of one person, from a static national archive to a living, county-by-county resource, in days rather than years. Contains Ordnance Survey data © Crown copyright and database right 2026. Historic county boundaries © Crown Copyright, RCAHMW, available under Open Government Licence 3.0.