Send MAV_CMD_DO_SET_ROI message to point camera gimbal at a 
    specified region of interest (LocationGlobal).
    The vehicle may also turn to face the ROI.

    For more information see: 
    http://copter.ardupilot.com/common-mavlink-mission-command-messages-mav_cmd/#mav_cmd_do_set_roi

def set_roi(location):
    """
    Send MAV_CMD_DO_SET_ROI message to point camera gimbal at a 
    specified region of interest (LocationGlobal).
    The vehicle may also turn to face the ROI.

    For more information see: 
    http://copter.ardupilot.com/common-mavlink-mission-command-messages-mav_cmd/#mav_cmd_do_set_roi
    """
    # create the MAV_CMD_DO_SET_ROI command
    msg = vehicle.message_factory.command_long_encode(
        0, 0,    # target system, target component
        mavutil.mavlink.MAV_CMD_DO_SET_ROI, #command
        0, #confirmation
        0, 0, 0, 0, #params 1-4
        location.lat,
        location.lon,
        location.alt
        )
    # send command to vehicle
    vehicle.send_mavlink(msg)