A method includes transmitting electrical signals between one or more pairs of body-surface electrodes attached to a body of a patient. Electrical potentials resulting from the transmitted electrical signals are acquired by an outer-facing electrode and an inner-facing electrode of a medical probe inserted in an organ of the patient. A proximity of the medical probe to surface tissue of the organ is estimated based on the electrical potentials acquired by the outer-facing electrode. A position of the medical probe within the organ is estimated based on the electrical potentials acquired by the inner-facing electrode.
