return expected mag vector

def expected_mag(RAW_IMU, ATTITUDE, inclination, declination):
    '''return expected mag vector'''
    m_body = Vector3(RAW_IMU.xmag, RAW_IMU.ymag, RAW_IMU.zmag)
    field_strength = m_body.length()

    m = rotation(ATTITUDE)

    r = Matrix3()
    r.from_euler(0, -radians(inclination), radians(declination))
    m_earth = r * Vector3(field_strength, 0, 0)

    return m.transposed() * m_earth