methods and systems method for sensing a position of an object in a body include positioning a probe in the body , making measurements of mapping electrical currents passing between at least a first electrode on the probe and a plurality of second electrodes on a surface of the body , calibrating the measurements so as to compensate for one or more non - ideal features of the measurements including effects of system - dependent electrical coupling to one or more devices other than the first electrode and the second electrodes , and computing the position of the probe in the body using the calibrated measurements .