We apply a look-up table technique to calibrate both position and orientation readings from a magnetic tracker for use in virtual environments within a defined working volume. In a test volume of 2.4 cubic meters, the method reduced the tracker's average position error by 79% and its average orientation error by 40%. We test the correction table against the tracker's performance outdoors (a metal-poor environment) and show that readings taken in our lab and corrected by our method exhibit less error than uncorrected readings taken outdoors. We demonstrate that such reduction in position error visibly improves registration in an augmented reality system, whereas the (lesser) reduction in orientation error does not visibly improve registration. We show that the model we used for the orientation error function was incorrect, preventing our method from achieving better correction of orientation error, We discuss future directions for correction of orientation error.