A method for detecting the presence of conductive objects, the method includes determining a characteristic frequency function of an undisturbed magnetic tracking system (14). The method includes measuring a disturbed real-time frequency function, and calculating real and imaginary components of the position indication signal using a chi-squared minimization of the disturbed frequency function to the undisturbed frequency function. The method also includes calculating a chi-squared value based on the characteristic frequency function und the disturbed frequency function, and monitoring the chi-squared value to detect changes indicating the presence of a conductive object.
