Ordnance Survey:
The views from a trig pillar can be worth the climb
Ordnance Survey:
Trig pillars provide a great spot to practice some yoga...
Ordnance Survey:
When trig pillars get a facelift...
Ordnance Survey:
Extreme weather and the trig pillar
Ordnance Survey:
Making a mark on a trig pillar
Ordnance Survey:
The view from a trig pillar
Ordnance Survey:
Building a trig pillar
Ordnance Survey:
Surveying from a trig pillar
Ordnance Survey:
The humble trig pillar