A system (20) for determining the position of a medical device (22) having a sensor (26) comprises a plurality of field radiators (56,58,60) wherein each field radiator has a plurality of radiator elements (32,34,36,38,40,42). Each radiator element generates a magnetic field such that each magnetic field is distinct from one another due to the use of a different frequency. The magnetic fields are measured by the sensor (26). The field radiators (56,58,60) and the sensor (26) are connected to a signal processor (25). The signal processor (25) includes an initial position estimator for establishing an initial position estimate for the sensor a magnetic field calculator for calculating the magnetic field at the initial position estimate a steepest descent calculator for calculating a steepest descent of the calculated magnetic field to the measured magnetic field and a new position estimate calculator for calculating a new position estimate of said sensor (26) based on said steepest descent. The signal processor (25) determines the position of the sensor (26) when the new position estimate of the sensor is within the desired range of accuracy for the system. Alternative field radiator arrangements are also provided in conjunction with a novel algorithm utilizing a global convergent technique.
