Abstract: A system to reduce VRU unreferenced heading drift error is disclosed. The VRU comprises an IMU and a processor, which hosts first and second modules for bias cancelation. The first module reads inertial data from the IMU when the VRU is powered on; determines whether the VRU is static for a time period; if the VRU is static, corrects gyroscope bias by subtracting an initial bias value from a previous bias value; sets a predefined initial yaw value. The second module reads inertial data from the IMU during in-run operation of the VRU; updates roll, pitch and yaw data, based on input data from a sensor fusion algorithm; outputs updated roll, pitch and yaw data; determines whether the VRU is static for a time period; and if the VRU is static, corrects the bias by subtracting a current bias value, multiplied by a predefined parameter, from a previous bias value.