A method and medical system for operating two leads disposed adjacent tissue of a patient. A first one of a pair of electrodes respectively carried by the two leads is activated to generate an electrical field within the tissue. An electrical parameter in response to the generated electrical field is measured at a second one of the pair of electrodes. A reference electrical parameter is measured in response to the generated electrical field at a reference electrode carried by the same one of the two leads that carries the first electrode. A reference distance between the first electrode and the reference electrode is known prior to the generation of the electrical field. The ratio between the measured electrical parameter and the measured reference electrical parameter is computed, and the distance between the pair of electrodes is computed as a function of the computed ratio and the reference distance.