Grotta Gigante horizontal pendulums

The Grotta Gigante horizontal pendulums are a pair of tiltmeters used for monitoring Earth movements, mounted in the Grotta Gigante in Italy. The horizontal pendulums, installed by the geodesist Antonio Marussi in 1959, are sensitive to deviations of the vertical, to rotations and shearing of the cave. The pendulum beam is suspended horizontally by two steel wires, an upper one fixed to the roof of the cave, the lower one fixed to the floor. The pendulum beam rotates in the horizontal plane around a virtual near-to-vertical axis that passes through the upper and lower mounting points.