A local positioning system uses at least one node to track a location of a mobile tag. The system measures flight times of signals communicated between the node and the tag to determine values indicative of the range of the tag from the node. If desired, the values may be filtered in an effort to increase the accuracy of the range estimation. As an example, a Kalman filtering algorithm may be used. Multiple antennas are used at both the node and the tag to provide more accurate range estimates and to determine when the tag is entering a dead zone where signals are blocked or attenuated by obstacles.