Similar to the way GPS provides for accurate positioning in a global sense, the proposed Phase I SBIR will provide a means of local positioning to millimeter accuracy. The approach will utilize several ultrasonic transmitters in fixed positions within a room or other confined area. Tiny receivers will be attached to the object to be tracked which may be for a instance a human arm. Signal processing of the signals received from each receiver will provide a 3D position relative to a reference. Measurement of the positions of each sensor along the arm in time will provide a dynamic characterization of body movement. Such device will have significant utility in NASA's virtual reality research and in particular to human motion characterization in robotic telepresence. During Phase I, a local positioning testbed will be developed using commercially available ultrasonic sensors. These will be interfaced to a DSP for waveform generation, phase comparison and x, y, z location solution and the feasibility of the concept evaluated. If successful, a Phase II effort would develop a portable device which would be evaluated under various environments and multiple applications. Commercialization would be initiated during Phase II and continue during Phase III. There would be significant demand for such a device in industrial manufacturing and home applications. Examples of commercial applications include an aid for the handicapped for navigating through buildings or a personnel tracking device for use in secure or dangerous workplaces.