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.

Black Combe, Cumbria, 600m (2,000ft)

Cadair Berwyn, Powys, 827m

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.

Criffel, Dumfries and Galloway, 569m

Garnedd Ugain, Gwynedd, 1065m

Great Whernside, North Yorkshire, 704m

Martinsell Hill, Wiltshire, 289m

Rottington, Cumbria, 141m

Snaefell, Isle of Man, 621m

The Stiperstones, Shropshire, 536m

Upton Beacon, Derbyshire, 538m

Winter Hill, Lancashire, 456m

Wyck Beacon, Gloucestershire, 250m

Yr Eifl, Gwynedd, 564m

All photographs copyright Stephen McCoy and Stephanie Wynne.