This thesis proposes a set of methods for the purpose of improving the calibration of three-axis magnetometers. Specifically, these methods aim to improve the accuracy of the bias estimation methods currently in use. The first proposed method utilizes a constrained optimization problem based on norm preserving. The second proposed method finds the same bias estimate as the first method, but in a computationally more efficient manner. The last proposed method tackles the case where the value of the local geomagnetic field is only imprecisely known. Computer simulations demonstrate the viability of the proposed methods.