AIS
OVERVIEW
What is the Automatic Identification
System (AIS)?
Picture a shipboard display system (e.g. radar, ECDIS, chart
plotter, etc.) with overlaid electronic chart data that includes
a mark for every significant ship within radio range; each
as desired with a velocity vector (indicating speed and heading).
Each ship "mark" could reflect the actual size of
the ship, with position to GPS or differential GPS accuracy.
By "clicking" on a ship mark, you could learn the
ship name, course and speed, classification, call sign, registration
number, MMSI,
and other information. Maneuvering information, closest
point of approach (CPA), time to closest point of approach
(TCPA) and other navigation information, more accurate and
more timely than information available from an automatic radar
plotting aid, could also be available. Display information
previously available only to modern Vessel
Traffic Service operations centers could now be available
to every AIS-equipped ship.
With this information, you could call any ship over VHF
radiotelephone by name, rather than by "ship off my port
bow" or some other imprecise means. Or you could
dial it up directly using
GMDSS equipment. Or you could send to the ship,
or receive from it, short safety-related email messages.
The AIS
[47 CFR 80.5, AIS Definition] is a shipboard broadcast system
that acts like a transponder, operating in the VHF maritime
band, that is capable of handling well over 4,500 reports
per minute and updates as often as every two seconds.
Shipboard AIS devices use either Self-Organizing Time Division Multiple Access
(SOTDMA) or Carrier-Sense Time Division
Multiple Access (CSTDMA) technology.
How Does AIS Work? >>
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