The aim of this paper is to integrate, among the common sensors from an inertial navigation system, a sensor to measure the magnetic field, magnetic field of the Earth. Basically, we want to integrate a digital compass, as an additional element for obtaining more accurate data as well as navigation. Advantages of using a magnetic sensor under a IMU (Inertial Measurement Unit) would be determining orientation of a device, relative to the axis of the Earth's magnetic field.