An object tracking system includes a plurality of tags. Each tag includes a mechanism for transmitting a triangulation signal and a position signal that is indicative of a change of position of the respective tag in a time period since a respective reset event. A plurality of triangulation stations receive the triangulation signals from the tags. At least one antenna receives the position signals from the tags. A computer is coupled to the triangulation stations and to the antenna. The computer is programmed to switch between (a) a first tag location algorithm to determine a current location of one of the tags using a differential time of arrival procedure based on the triangulation signal, and (b) a second tag location algorithm to determine a current location of the tag based on the position signal transmitted by the tag and a previous known location of the tag.