A method for dynamically initializing a 3 degrees of freedom (3DOF) tracking device is described. In one aspect, the method includes accessing a gyroscope signal from a gyroscope of the 3DOF tracking device, accessing an accelerometer signal from an accelerometer of the 3DOF tracking device, determining an initial state includes a combination of an initial orientation, an initial position, and an initial velocity of the 3DOF tracking device, the initial state indicating a starting condition of the 3DOF tracking device, integrating the gyroscope signal and the accelerometer signal to obtain orientation and position signals using the initial state, and refining an inclination signal of the orientation signal using the position signal.