A method enables a gas turbine engine to be assembled. The method includes determining a normalized impedance curve for the transducer, determining a time rate of change of the normalized impedance of the transducer along a line of constant gap, and correcting an apparent gap magnitude using the determined time rate of change. As a result, the vehicle position and velocity are determined accurately in the event of undocking and re-docking of the mobile device from a docking system in the vehicle.