def cartesian_to_heading(cartesian_angle):
    """
    Cartesian orientation (CCW from east) to heading (CW from north)

    :param cartesian_angle: CCW from East, in degrees
    :type cartesian_angle: float
    :returns: heading direction, CW from North, in degrees
    :rtype: float
    """
    return 90 - cartesian_angle;