We climbed up to the monument above Leswalt in the Rhins of Galloway. It's an excellent viewpoint, looking out over the sea to Ireland and back across Loch Ryan to Stranraer. That's why there is a trig point up there. I've blogged before about benchmarks and their use in map making. The Ordnance Survey apparently started putting in triangulation pillars from 1935 onwards. That's much later than I thought. The aim is to be able to see 3 other pillars from the one you are at and to measure angles and distances. Height can be done by measuring angles up and down as well. So somewhere in the photographs there is probably another trig point, but I don't know exactly where to look!
