The Sliding Pipe Underground Detector is an innovative technology for detecting underground movements and a simple alternative to costly electronic inclinometer installations. For use by non-technical personnel, these are designed on a site specific base to detect deflection of a predetermined amount of movement. The SPUD uses a simple (non-electronic) dedicated sliding sensor which stays permanently inside a pipe installed in the ground. An assessment of the movement can be made within seconds at any time without the need for any external equipment.