A system and method are provided for determining characteristics of a device electrode disposed on a medical device within a body. A plurality of measurement electrodes are coupled to an external surface of the body and establish transmission paths for current through the body. An electronic control unit (ECU) is configured to cause transmission of current between a pair of active electrodes selected from the measurement electrodes and thereby generate a voltage on the device electrode. The ECU receives impedance signals from a plurality of passive electrodes among the measurement electrodes other than the active electrodes. The ECU establishes a virtual reference electrode at a reference position within the body responsive to the impedance signals and computes a position of the device responsive to the voltage on the device electrode and the reference position of the reference electrode. The ECU may also compute impedances at the device and measurement electrodes.