Abstract: A method and system for measuring wear in the lining of a vessel in which undirected radiation signals are transmitted by at least two transmitters at known positions to a receiver at the device for measuring wear. The distances between the transmitters and receiver are determined based on the time of flight of the radiation between the transmitters and receiver. The location of the receiver at the measuring device is determined to be at a point on an arc of points at the distance calculated based on the time of flight of the signal from each of the transmitters to the receiver. The receiver is determined to be at the intersection of the two arcs of points at the distance calculated based on the time of flight of the signal from the each of the transmitters.