Definition of "extensometer"

For the ground, that means using three primary types of equipment:■ Extensometers to look for ground heave - the upwards movement of soil, which can occur at any stage. It is essentially the opposite of erosion and is often associated with clay-type soils which swell when wet.■ Inclinometers, which measure slope movements.■ Piezometers to measure water levels.

2022 October 5, Tom Allett, “HS2's green screen to aid the environment”, in RAIL, number 967, page 35