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A deeply founded pillar anchoring the levelling network.
Also known as: FBM benchmark, Primary levelling benchmark
A fundamental benchmark is a deeply founded concrete pillar with buried and surface marks, sited on stable ground to anchor the national levelling network against ground movement.
Anchors the national levelling network at a point chosen for the stability of its ground.
Contexts: Maps
Carries a buried mark as well as a surface one, so movement of the surface can be detected by comparing the two — the pillar checks itself.
Contexts: Maps
A low concrete pillar with a chamber below it, carrying a metal plate at the surface and a second mark buried beneath.