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Route Message

Introduction/Additional information: 

The Route Message Broadcast is used as a means to indicate intended navigation and route information to nearby ships, allowing ships to avoid ending up in a close quarter situation where the involved ships have to comply with the COLREG rules. The current and a fixed number of coming route legs of the monitored route is shared with other ships.

On-board message flow

The ECDIS initiates any Route Message broadcast to be transmitted by the Communication Device, as well as any Route Message interrogations. The ECDIS will compile the Route Message data payload, or interrogation message payload, as defined in section 4, and send a BBM or ABM message with the payload to the Communication Device.

The Communication Device will provide the ECDIS with VDM-message data as they are received on the VHF data links.

VDM message payloads may be:

  • Remote AIS target dynamic, static and voyage data (AIS Msg 1,2,3,5,9,18,19,24A,24B)
  • Remote ship route message data (AIS msg 8 or VDES ASM msgs)
  • Route Message interrogation messages (AIS msg 6 or VDES ASM msgs)

The Route Message-payload is defined such that the current leg as well as up to twelve additional legs can be shared, with Cross Track Distance (XTD) parameters for each leg.

When no Monitored Route is active, the Route Message shall have an empty payload.

Two Route Messages are defined, depending on the communication system used. VDES ASM channel communication allows for a higher bitrate, and more data within the three timeslot limit.

Leg parameters (planned speed, XTD, geometry) are for the leg ending at the waypoint following those parameters. Turn radius is for the next waypoint

Permitted as from: 
03/03/2016
Registrant: 
STM project (Sweden)
Physical link: 
AIS
Message number (0=VDES-VDE): 
8
DAC or VPFI: 
265
FI / Message ID: 
1
State: 
in force
Number of slots (max): 
3
Last modified: 
29/01/2021 - 23:19
Reporting Rate: 

Message broadcast trigger events

The message shall be broadcast so that ships in receiving range has accurate information at a reasonable delay, without creating unnecessary load on the VHF datalinks.

A new Route Message broadcast shall be initiated by ECDIS when any of the below events occurs:

  • Six minutes have passed since last Route Message broadcast
  • A Route Message interrogation was received and over one minute has passed since last Route Message broadcast on that channel
  • Any of the data in the last Route Message broadcast has been changed
  • When passing a waypoint (after completing the turn, see Annex A for definition)
  • The Monitored Route has been deactivated
  • A Monitored Route is activated

The Route Message broadcast shall be initiated by the ECDIS as soon as possible after any of the above broadcast triggers.

There shall be no autonomous Route Message broadcasts when there is no Monitored Route active in ECDIS, except for one additional Route Message transmission after stopping a Monitored Route. The system shall however respond to interrogations, with an empty route message. If the ship has had a speed below 1 (one) knot for more than 6 minutes no route message shall be broadcasted

Route segmentation for AIS broadcasts

The Route Message-payload is defined such that up to seven legs can be shared. The first leg shared during a turn shall be the leg leading up to the turn, otherwise it shall be the current leg. If any of the waypoints within the seven legs are over 200 NM (max ±209.7151’) from the previous waypoint, this will be treated as the last WP in the currently shared monitored route segment, or a virtual FROM waypoint inserted.

Details: 

 

Parameter

Bits

Description

Comment

Message ID

6

Identifier for Message 8; always 8

 

Repeat indicator

2

Used by the repeater to indicate how many times a message has been repeated.

 

Source ID

30

MMSI number of source station

 

Spare

2

Not used. Should be set to zero. Reserved for future use

 

DAC

10

DAC = 26510 = 01000010012

 

FI

6

Function identifier = 110 = 0000012

 

If no monitored route is available the message ends here

First waypoint type

1

0 = Navigating away from first waypoint (on route)

1 = Navigating towards first waypoint (start of route)

 

First waypoint longitude

28

Longitude in 1/10 000 min (±180°, East = positive (as per 2’s complement), West = negative (as per 2’s complement).

181° = (6791AC0h) = not available = default)

Standard AIS format

First waypoint latitude

27

Latitude in 1/10 000 min (±90°, North = positive (as per 2’s complement), South = negative (as per 2’s complement).

91° (3412140h) = not available = default)

Standard AIS format

Intermediate legs

(64)

Repeats 0 … 6 times depending on total number of legs

Leg geometry

1

0 = Loxodrome (Rhumb line)

1 = Orthodrome (Great circle)

 

Planned speed

10

Planned speed over ground in 1/10 knot steps (0-102.2 knots)

1 023 = not available, 1 022 = 102.2 knots or higher

Standard AIS format

Turn radius

9

Turn radius in 1/100 NM. 0 = not available

Max 5.11 NM

Longitude delta

22

Longitude difference from previous waypoint in 1/10 000 min. East = positive, West = negative (as per 2’s complement).

Max ±209.7151’

Latitude delta

22

Latitude difference from previous waypoint in 1/10 000 min. East = positive, West = negative (as per 2’s complement).

Max ±209.7151’

Final reported leg

(66)

 

Leg geometry

1

0 = Loxodrome (Rhumb line)

1 = Orthodrome (Great circle)

 

Planned speed

10

Planned speed over ground in 1/10 knot steps (0-102.2 knots)

1 023 = not available, 1 022 = 102.2 knots or higher

Standard AIS format

Last waypoint longitude

28

Longitude in 1/10 000 min (±180°, East = positive (as per 2’s complement), West = negative (as per 2’s complement).

181° = (6791AC0h) = not available = default)

Standard AIS format

Last waypoint latitude

27

Latitude in 1/10 000 min (±90°, North = positive (as per 2’s complement), South = negative (as per 2’s complement).

91° (3412140h) = not available = default)

Standard AIS format

 

Steering mode

2

0 = Manual (default)

1 = Heading control

2 = Track control

3 = Reserved for future use

 

Spare

4

Padding to bring total message length to a byte boundary.

Always 0

Required for AIS
How portrayed: 
  1. ANNEX A – AIS Route Broadcast Logic
    1. Standard AIS Route Broadcasts

Standard AIS route broadcast are used when all route segments are less than delta LAT & LON limits (max ±209.7151’), otherwise see 5.2 nedan.

Regular Conditions

Transmitter (ECDIS)

Receiver (ECDIS): Transmitting ship at step 1

 

Step 1. Own ship position is on the straight part of leg. Transmitter (ECDIS) uses the standard broadcast trigger events:

  • FIRST WP: “WP0”
  • Following WPs: Max 7 Waypoints / 6 Route legs ahead, including turn radiuses (if available).

 

Step 2. Own ship passing ‘SOT’ (Start Of Turn line):

  • No additional broadcast event.

 

Step 3. Own ship sailing on curve (i.e. on turn radius). No additional broadcast events, except the periodic broadcast interval (every 6 minutes) which may be reached since last Route Message broadcast, in that case (same as Step 1):

  • FIRST WP: “WP0”
  • Following WPs: Max 7 Waypoints / 6 Route legs ahead, including turn radiuses (if available).

 

Receiver (ECDIS): Transmitting ship at step 3

 

Step 4. Own ship passing ‘EOT’ (End Of Turn line). The ‘WP passing’ event is triggered, resulting in:

  • FIRST WP: “WP1”
  • Following WPs: Max 7 Waypoints / 6 Route legs ahead, including turn radiuses (if available).
  • Previous “WP0” is not broadcast anymore and removed from the receiver ECDIS chart area including the WP1 radius.

 

Receiver (ECDIS): Transmitting ship at step 5

 

Step 5. Same as Step 1 above.

 

    1. AIS Route Exceptions for Long Legs

Due to the AIS Route message representation of intermediate waypoints in delta LAT & LON format very long legs (> ±209.7151’) must be reported differently. Depending on the ship position either the broadcast AIS route contains fewer legs, or a virtual waypoint on the current leg is used to allow additional legs to be reported, in accordance the sections below.

The virtual waypoint shall be inserted on the current leg so that future legs can be reported in ample time before reaching them, ideally as far away from the leg end waypoint as the delta LAT & LON format (≤ ±209.7151’) allows.

      1. Length of the current route leg is more than delta LAT & LON limits.
        Own ship distance to WP1 is more than delta LAT & LON limits.

WP0-WP1: Delta LAT & LON > ±209.7151’

Transmitter (ECDIS)

Receiver (ECDIS): Transmitting ship at step 1

 

Step 1. Own ship position is on the straight leg, WP0-WP1 delta LAT & LON > ±209.7151’. Ship’s distance to WP1 is also more than LAT & LON > ±209.7151’. Transmitter (ECDIS) uses the standard broadcast trigger events (every 6 minutes). AIS Route Message broadcast:

  • FIRST WP: “WP0”
  • LAST WP: “WP1”

 

      1. Length of the current route leg is more than delta LAT & LON limits.
        Own ship distance to WP1 is less than delta LAN & LON limits.
        WP1-WP2 delta LAT & LON > ±209.7151’ limits.

WP0-WP1: Delta LAT & LON > ±209.7151’
WP1-WP2: Delta LAT & LON > ±209.7151’

Transmitter (ECDIS)

Receiver (ECDIS): Transmitting ship at step 1

Step 1. A regular broadcast event occurs and the own ship has passed the Virtual Waypoint (the ship’s distance to Waypoint 1 is less than LAT & LON ±209.7151’). There shall be no additional broadcast due to passing the Virtual Waypoint, but any broadcast after passing the waypoint shall use the Virtual Waypoint as the FIRST WP:

  • FIRST WP: “VWP”
  • SECOND WP: “WP1”, delta LAT & LON between VWP and WP1 is less than ±209.7151’
  • LAST WP: “WP2”

 

Step 2. Own ship passing ‘SOT’ (Start Of Turn line):

  • No additional broadcast event.

 

Step 3. Own ship sailing on curve (i.e. on turn radius). No additional broadcast events, except the periodic broadcast interval (every 6 minutes) which may be reached since last Route Message broadcast, in that case:

  • FIRST WP: “VWP”
  • SECOND WP: “WP1”, delta LAT & LON between VWP and WP1 is less than ±209.7151’
  • LAST WP: “WP2”

 

Step 4. Own ship passing ‘EOT’ (End Of Turn line). The ‘WP passing’ event is triggered resulting in:

  • FIRST WP: “WP1”
  • LAST WP: “WP2”, no more waypoints because delta LAT & LON between WP1 and WP2 is more than ±209.7151’
  • Previous “VWP” is not broadcast anymore and removed from the receiver ECDIS chart area including the WP1 radius.

 

Step 5. Same as 5.2.1 ovan.

 

 

      1. Length of the current route leg is more than delta LAT & LON limits.
        Own ship distance to WP1 is less than delta LAT & LON limits.
        WP1-WP2 delta LAT & LON is less than ±209.7151’ limits.

WP0-WP1: Delta LAT & LON > ±209.7151’

Transmitter (ECDIS)

Receiver (ECDIS): Transmitting ship at step 1

 

Step 1. A regular broadcast event occurs and the own ship has passed the Virtual Waypoint (the ship’s distance to Waypoint 1 is less than LAT & LON ±209.7151’). There shall be no additional broadcast due to passing the Virtual Waypoint, but any broadcast after passing the waypoint shall use the Virtual Waypoint as the FIRST WP:

  • FIRST WP: “VWP”
  • Following WPs: Max 7 Waypoints / 6 Route legs ahead, including turn radiuses (if available).

 

Step 2. Own ship passing ‘SOT’ (Start Of Turn line):

  • No additional broadcast event.

 

Step 3. Own ship sailing on curve (i.e. on turn radius). No additional broadcast event, except the periodic broadcast interval (every 6 minutes) which may be reached since last Route Message broadcast, in that case:

  • FIRST WP: “VWP”
  • Following WPs: Max 7 Waypoints / 6 Route legs ahead, including turn radiuses (if available).

 

Step 4. Own ship passing ‘EOT’ (End Of Turn line). The ‘WP passing’ event is triggered, resulting in:

  • FIRST WP: “WP1”
  • Following WPs: Max 7 Waypoints / 6 Route legs ahead, including turn radiuses (if available).
  • Previous “VWP” is not broadcast anymore and removed from the receiver ECDIS chart area including the WP1 radius.

 

Receiver (ECDIS): Transmitting ship at step 5

 

Step 5. Standard broadcast rules, see 5.1 ovan.

 

Attachment: 
PDF icon route-message-system-requirementsg1.pdf