This IFM should be used by a VTS to advise its waypoints and/or its route plan. If the VTS uses this IFM 18 within an addressed binary message, then the waypoints and/or the route plan will be available to the addressed recipient, one ship, only. If the VTS uses this IFM 18 within a broadcast binary message, then the information will be available to all other ships in the VTSs vicinity.
When transmitting, the VTS should include up to 12 advised waypoints and/or a route specified by a textual description, if available. If waypoints are transmitted, then a recommended turning radius may be transmitted for each waypoint.
|Number of bits||Description|
|AWP||4||Number of advised waypoints (1-12); 0 = no waypoint = default; 12-15 = not used|
|WP i.Lon||28||Longitude of advised waypoint i in 1/10 000 min (±180°, East = positive, West = negative). Field required if and as often as 1 ≤ i ≤ AWP, i = 1, 2, 3, …, 12; field not required if AWP = 0|
|WP i.Lat||27||Latitude of advised waypoint i in 1/10 000 min (±90°, North = positive, South = negative). Field required if and as often as 1 ≤ i ≤ AWP, i = 1, 2, 3, …, 12; field not required if AWP = 0|
|Advised turning radius i||12||Advised turning radius at advised waypoint i in metres; 0 = not available = default; 1-4 095 m. Field required if and as often as 1 ≤ i ≤ AWP, i = 1, 2, 3, …, 12; field not required if AWP = 0|
|Advised route specified by textual description||120||Description of the advised route in textual form, e.g. —west channel“; maximum 20 characters using 6-bit ASCII; @@@@@@@@@@@@@@@@@@@@ = not available (field must not be omitted)|
|Spare||AWP||Bits||Spare. Not used. Should be set to zero|
|Number of bits||128-928||The number of bits of the IFM 17 may be calculated as follows: 124 + (AWP × 67) + spare|
|Number of next waypoints transmitted||0||1||2||3||4||5||6||7||8||9||10||11||12||13||14|
|Number of slots used for this message||2||2||2||3||3||3||3||4||4||4||4||5||5||5||5|