A method includes retrieving from a memory a stored sensitivity table that associates magnetic position sensor readings with measured magnetic fields. One or more calibration values for the magnetic position sensor are estimated during a catheterization procedure in which a magnetic position sensor, fitted at a distal end of a catheter, is placed in an organ of a patient, based on (i) the stored sensitivity table and (ii) readings acquired by the magnetic position sensor while in the organ. Based on the one or more calibration values, a location of the distal end in the organ is magnetically tracked.
