The marks the retriangulation actually used — pillars, bolts, buried blocks, church spires — from the Ordnance Survey archive
Gold = concrete pillar. Blue = bolt/rivet/centre. Purple = church spire, flagstaff, chimney. Grey-brown = buried block. Faded = marked destroyed in the archive. This is the survey network, not a bagging list of standing pillars. Downloads follow the filters (so “pillars only” plus “hide destroyed” is a usable GPS list). To see the ground around a mark: pick a station, then Compare and drag the gold bar along the bottom of the map.
Between 1935 and 1962 the Ordnance Survey retriangulated Great Britain. The familiar concrete pillar is only one kind of station. The network also used bolts and rivets in rock, buried blocks, and existing structures — church spires, flagstaffs, chimneys — as intersected points. This map is that archive clipped to ceremonial Wiltshire (including Swindon) using OpenStreetMap’s county outline, from OS’s published complete trig list.
It is not a list of pillars you can still stand on. Many stations are destroyed; many were never pillars. Condition and “logged today” live on TrigpointingUK. Coordinates are the original archive values (not OSTN15), typically within about 0.1 m for first- to third-order stations — close enough to find the mark. The map layers are OpenStreetMap, Environment Agency 1 m LiDAR hillshade (DSM and DTM, Open Government Licence), and Esri World Imagery. Compare puts satellite on the left and DTM hillshade on the right.
1 primary, 2 secondary, 3 tertiary, 4 minor / map detail. Lower numbers were observed more carefully and hold the network together.