Skip to main content

Trig Points: The Basis for Modern Mapping

Part of the Mapping the Past trail

Trig Point at Hill of Kilncadzow

It’s 80 years since Trig Points were first used to Map the Nation. They were designed by Brigadier Martin Hotine to assist in the re-triangulation of Great Britain. The re-triangulation needed fixed points located across the whole country, which could be used to mount survey instruments. From each of these points it was possible to see at least two other Trig Points on a clear day. 

Using TRIGonometry, a system of triangles could be established between these points and across the nation. From these triangles accurate measurements of features and buildings could be taken, allowing for more detailed mapping than had been possible before. 

6500 Trig Points were erected across the whole of the UK and five survive in and around the Clyde and Avon Valley. These can be found at: 

Trig Point Name Trig Point Number OS Grid Reference
Blackhill TP1414 NS 832 433
Hill of Kilncadzow TP4206 NS 888 487
Headshill TP3699 NS 715 477
Marshill TP4676 NS 784 452
Milton Head TP4842 NS 825 495


All of these sites are accessible, but both Marshill and Hill of Kincadzow are located in farmland and due care and attention must be taken when visiting.  Please follow the Scottish Outdoor Access Code. 

Blackhill is a National Trust for Scotland property and is accessible up a rough farm track.  Miltonhead is located on Milton Road, to the west of Carluke.  There are limited parking spaces, but it is easily accessible. Headshill is located close to the road towards Wellgreen Farm at Heads, just north of Glassford, and is enclosed by fence. Please take care when stopping to view this site.

Map of Trig Points in and around the Clyde and Avon Valley.

This listing was created as part of the Mapping the Past project, managed by Northlight Heritage and delivered by CAVLP Heritage. Explore the site as part of the Mapping the Past trail (see right).

Area Guide