If you spend time wandering around the UK, you will undoubtely have come across a concrete strucure like this one in Maryhill Park in Glasgow. They are trig pillars, and they were first used to map Britain in 1936. Trig pillars are set at known locations and at known altitude, and have a brass fitting ln the top (called a spider) to hold a theodolite or other mapping equipment.
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#glasgow #trigpoint
#trigpillar
#trigpillarbagging #maryhillpark
