Abstract: A handheld device (200) includes a housing (202) having a cylindrical bore (204) therein and which terminates at a distal end (206) of the housing with a central orifice communicating therewith. The housing serves for receiving a portion of a body of a drawing implement with its drawing tip extending from the central orifice. The device (200) further includes an ultrasonic receiver or transmitter (220) mounted within the housing, remote from the drawing tip, yet in close proximity with the bore. This device serves for receiving or transmitting an intermittent ultrasound signal through the bore and the plurality of openings, thereby enabling triangulation of the drawing tip.

Abstract: A method and corresponding system for tracking variations in distance D calculated from time-of-flight measurements of a sequence of pulses of a pressure wave oscillation from a transmitter to a receiver identifies a state of synchronous operation by obtaining at least two time-of-flight measurements derived from successive pressure wave pulses which satisfy given synchronicity criteria. Successive time-of-flight measurements are then monitored to identify a shifted time-of-flight measurement which varies by at least half of the wave period from a predicted time-of-flight value calculated from a number of preceding time-of-flight measurements. A shift factor is then identified corresponding to an integer multiple of the wave period by which the shifted time-of-flight measurement must be corrected to obtain a corrected time-of-flight measurement falling within half of the wave period from the predicted time-of-flight value.