Area Notice

Introduction/Additional information: 

The purpose of the Area Notice is to transmit information that pertains to a region or area, for example a security zone, an area of fog, or dredging operations. The areas that are being defined can be circles, rectangles, polygons, or sectors. They can also be defined as a simple point or series of points (polyline). The Area Notice message can be made up of multiple subareas in which case the total area is the union of the subareas. This message can also be used to convey advisory lines or tracks (using the polyline subarea); however, the Route Information message should be used for recommended or directed routes.

An Area Notice should be used to broadcast dynamic information (i.e., information that is time- dependent). These messages are to be used for a specific time period, and will automatically timeout at the end of the period. If the Area Notice must be in place longer, then a new Area Notice must be transmitted with a new start and end time. It should be only used to convey pertinent time-critical navigation-safety information to mariners or authorities, and not as a means to convey information already provided by official nautical charts or publications.

Usage Notes

  1. The information is time-dependent (i.e., has start date/time and duration). If an Area Notice (except for a cancellation message – Area Type 126) is received without a valid start date/time and duration then it should be discarded.
  2. When the current month is December and the notice start month is January, the notice start year shall be the current year plus one; the notice start year shall be the current year in all other cases.
  3. The message may be transmitted prior to the start time/date to allow for advance notice. To avoid confusion, it should not be transmitted more than one day in advance.
  4. The message should not be transmitted beyond the designated end date/time except for a cancellation message. A cancellation message can be transmitted before the designated end date/time using the same Message Linkage ID with an Area Type of 126 (cancellation), a Duration = 0, and start time fields all set to “not available.”
  5. Presentation software should automatically remove the area notice from the display after the end date/time or upon receipt of a cancellation message.
  6. Up to 5-slot messages can be created, but messages with more than three slots should be avoided. Messages with more slots are less likely to be received due to RF noise or packet collision.
  7. A circular sub-area (Type 0) with a zero radius (scale factor should also be set to 0) is a point that can be used as a node in a polygon. This is used when more precision is needed than is possible using the points in thepolygon subarea (the trade-off is more subareas and a longer message).
  8. Polygon sub-areas (Type 4) must follow immediately after a circle/point sub-area (Type 0 sub-area with 0 radius) in the same Area Notice message. The point defines the start of the line segments. If more than five points are needed for a polygon, then additional polygon sub-areas can be used. However, they must follow immediately after the first polygon sub-area and be contained in the same Area Notice message.
  9. A rectangular sub-area (Type 1) with a zero for both North and East dimensions (scale factor and orientation should also be set to 0) is a point that can be used as a waypoint or to define a line. This is used when more precision is needed than is possible using the points in the polyline subarea (the trade-off is more subareas and a longer message).
  10. Waypoints can be specified using the polyline/waypoint sub-area (Type 3). If more precision is needed then multiple rectangle/point sub-areas (Type 1 sub-area with 0 North and East dimensions) can be used (e.g., one for each waypoint).
  11. When waypoints are specified using polyline or rectangle/point sub-areas, they should be numbered/used in the order that they appear in the message.
  12. Polyline sub-areas (Type 3) must follow immediately after a rectangle/point sub-area (Type 1 sub-area with 0 for North and East dimensions) in the same Area Notice message. The point defines the start of the line segments. If more than five points are needed for a polyline, then additional polyline sub-areas can be used. However, they must follow immediately after the first polyline sub-area and be contained in the same Area Notice message.
  13. The polygon sub-area (Area Shape 4) should be used to create polygon areas. However, if more precision is needed to specify the points in the polygon then the circle/point sub-area (Type 0 with radius set to zero) can be used, one sub-area per point. All points (sub-areas of Type 0) must occur in sequence and be contained within the same message. The polgon is formed by connecting the points and closing the shape from the last point back to the first.
  14. Distances and bearings between points in the Area Notice should be calculated using Rhumb lines not Great Circles.
  15. The Message Linkage ID and the first six digits of the source MMSI can be used to link additional text (e.g., a separate Text Description message). This information must be included in both the Area Notice and additional Text Description message.
  16. The total area defined by one Area Notice (one Message Linkage ID) is the union of all of the sub-areas contained in the message.
  17. If the same Message Linkage ID is retransmitted with different sub-areas and/or times the presentation software should replace the old Area with the new.
  18. The Message Linkage ID must be unique across all ASMs to which it applies. In this way, the Message Linkage ID and Source MMSI are connected to the same text message.
Registrant: 
USCG RDC
Message number: 
8
DAC: 
366
FI: 
22
State: 
deprecated
Number of slots (max): 
5
Reporting Rate: 
Reporting rate is an operational decision - nominally at 5 minute intervals.
How portrayed: 

Areas should be displayed as graphical overlays along with accompanying text.

Permitted as from: 
12/04/2011
Technical point of contact: 

Dr. Gregory Johnson, gwjohnson@alionscience.com

Details: 

 

  Parameter # of bits Description
Standard Message Header 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. (See ITU-R M.1371-3, Annex 2, § 4.6.1).0 – 3; 0 = default; 3 = do not repeat any more. Set to 0 (default).
Source MMSI 30 MMSI number of source station. This varies according to the transmitter ID.
Spare 2 Not used. Set to zero
Binary Data Designated Area Code 10 Designated area code (DAC). (See Rec. ITU-R M.1371-3 § 2.1, Annex 5). Set to 366 (US).
Function Identifier 6 Function identifier. Set to 22
Application Data Message Linkage ID 10 A source specific running number, unique across all binary messages equipped with Message Linkage ID. Used to link additional information to the message by a Text Description message. The Message Linkage ID and the first six digits of the source MMSI uniquely identify the sent message. 1 – 1,023; 0 = not available = default.
Notice Description 7 Notice Description as per Table 11.
Set to 0 – 127 according to description. If 127, there must be associated text (see Table 10).
Start time of Area UTC month 4 UTC month of the Area start. 1 – 12; 0 = UTC month not available = default; 13 – 15 (reserved for future use).
UTC day 5 UTC day of the Area start.1 – 31; 0 = UTC day not available = default.
UTC hour 5 UTC hour of the Area start. 0 – 23; 24 = UTC hour not available = default; 25 – 31 (reserved for future use).
UTC minute 6 UTC minute of the Area start.0 – 59; 60 = UTC minute not available = default; 61 – 63 (reserved for future use.)
Duration 18 Minutes until end of Area Notice, measured from start time of Area Notice. Maximum duration is 262,142 minutes (182.04 days).0 = cancel Area Notice; 1 – 262,142; 262,143 = undefined = default.
Sub-area 1 90 Area description, structured as in 
Table 5 - Table 10. A short text description may be associated with the areas using Sub-area 5: Associated text. 2-slot message.
Sub-area 2 90 Optional additional area, structured as in 
Table 5 - Table 10. 2-slot message.
Sub-area 3 90 Optional additional area, structured as in 
Table 5 - Table 10. 3-slot message.
Sub-area 4 90 Optional additional area, structured as in 
Table 5 - Table 10. 3-slot message.
Sub-area 5 90 Optional additional area, structured as in 
Table 5 - Table 10. 3-slot message.
Sub-area 6 90 Optional additional area, structured as in 
Table 5 - Table 10. 4-slot message.
Sub-area 7 90 Optional additional area, structured as in 
Table 5 - Table 10. 4-slot message.
Sub-area 8 90 Optional additional area, structured as in 
Table 5 - Table 10. 5-slot message.
Sub-area 9 90 Optional additional area, structured as in 
Table 5 - Table 10. 5-slot message.
Sub-area 10 90 Optional additional area, structured as in 
Table 5 - Table 10. 5-slot message.
Spare 1-7 From 1 to 7 spare bits, added to make the total message length an even number of bytes. Set all spare bits to 0.
Total 208 – 1016 2-5 slot message