The triangulation points that mapped Britain

In 1936, the Ordnance Survey began to construct concrete triangulation pillars, or trig points, to aid accurate measurement and map-making using the principles of trigonometry. By 1962, more than 6,000 had been built. And Stephen McCoy and Stephanie Wynne are trying to photograph the 310 primary pillars still standing.

Image caption, Black Combe, Cumbria, 600m (2,000ft)
Image caption, Cadair Berwyn, Powys, 827m
Image caption, Cold Ashby, Northamptonshire, 210m

The pillars were built in positions where at least two other points could be seen in order to form triangles for accurate measurement.

McCoy and Wynne's work comprises large 360-degree panoramic photographs produced by placing the camera on top of the triangulation pillar, alongside a picture of the pillar itself.

Image caption, Criffel, Dumfries and Galloway, 569m
Image caption, Garnedd Ugain, Gwynedd, 1065m
Image caption, Great Whernside, North Yorkshire, 704m
Image caption, Martinsell Hill, Wiltshire, 289m
Image caption, Rottington, Cumbria, 141m
Image caption, Snaefell, Isle of Man, 621m
Image caption, The Stiperstones, Shropshire, 536m
Image caption, Upton Beacon, Derbyshire, 538m
Image caption, Winter Hill, Lancashire, 456m
Image caption, Wyck Beacon, Gloucestershire, 250m
Image caption, Yr Eifl, Gwynedd, 564m

All photographs copyright Stephen McCoy and Stephanie Wynne.