1. A method for adjusting parameters of a calibration model in a medical position sensing system prior to tracking a medical instrument, the position sensing system including a sensor for obtaining a measurement indicative of a location of an object, the method comprising: a) providing an initial set of model parameters for determining a relationship between a sensor measurement and a location value within a predetermined three-dimensional tracking volume of location values; b) selecting a plurality of sub-volumes of location values within the range of location values; c) providing for each of the selected plurality of sub-volumes of location values a local set of model parameters for determining a relationship between a sensor measurement and a location value within the selected sub-volume of location values; d) obtaining a measurement from the sensor; e) determining an estimate of the location of the object from the sensor measurement and the initial set of model parameters; and f) identifying, using the position sensing system, at least one of the selected sub-volumes of location values related to the estimate of the location of the object.