Updated on 13th April 2010

List of Slides
Slide AIS 1

The Flow

 What is AIS?
 What is its use?
 How did the need for this equipment
arise?
 How does it work?
 Its capabilities
 Its limitations.
Slide AIS 2

What is AIS?

AIS
Stands for Automatic Identification System

Automatic
No human Intervention once the system


is set and gets going.

Identification
Identification of the other ships which


are also operating the AIS.

System
Your AIS is a part of system which


includes your ship, ships around you

who are also operating AIS, VTS and
various Navigational subsystems like
GPS, Log, Gyro etc.
Slide AIS 3

What is its use?

It helps a vessel's watch keeping officer and the VTS
to Identify and monitor movement of vessels in the
vicinity.

In this system, a ship exchanges data like

Her identity, Position, Course, and Speed
electronically with other nearby ships and VTS
stations.

The same data received form other is displayed on a

screen in the wheel house for the benefit of the
officer of the watch.

The IMO requires AIS to be fitted aboard

international voyaging ships with GT of 300 or more
and all passenger ships regardless of size.

It is estimated that more than 40,000 ships currently

carry AIS class A equipment.
Slide AIS 4

How did the need arise?

OOW has to continuously watch out against the danger of
collision.

The OOW continuously monitors movements of

ships around to avoid close quarter situation.

He uses visual, aural or electronic means to carry

out this monitoring.

Such monitoring becomes inadequate if movement and

intention of another vessel are unclear.

It then becomes very critical to communicate with

such a ship.

With number of ships in the vicinity, confusion

about a ships identity can be dangerous.

The need to positively identify a ship has became more

urgent because of presence of faster and larger ships,
increasing traffic density and zero tolerance for pollution
which invariably occurs after a collision.

AIS provided the solution for easy identification.

Slide AIS 5

Applications of A I S

Over the years, more and more uses of this

equipment have been found and currently
it is being used for :-
 Collision avoidance
 Vessel traffic services
 Aids to navigation with virtual Buoyage.
 Search and rescue
Slides AIS 6

Collision avoidance

AIS is used in navigation primarily for

collision avoidance.

Currently this system is being used as a

supplement to other anti-collision aids.

It should not be mistaken as an

automated collision avoidance system.
Slide AIS 7

Vessel Traffic Service

AIS has provided great value addition to VTS

operations.

In busy waters and harbours, a local Vessel

Traffic Service (VTS) controls and monitors
ship traffic.

The VTS maintains a radar plot on which every

ship in the harbour is tracked.

In the past, identity of a vessel was established

only after receiving a RT report from the ship.

This was a time confusing task which was

prone to delay and errors because of difficulty
in RT communications due to language and
accents difficulties.

AIS has done away with such RT reports. With

AIS, identity as well as various navigational
data of the ships is provided digitally on
continuous basis.
Slide AIS 8

Aid to Navigation
Using the AIS technology, it is now possible to
digitally inject data in a ships radar to create a
virtual navigational mark.
For example, if a navigational buoy has been
damaged or drifted away, the shore authorities
can now inject a virtual buoy in to ships radars
and electronic charts through AIS.
Isolated dangers in the middle of the sea, where
buoyage can be uncertain and expensive, virtual
buoyage can provide a rapid and economical
solution.
The US Coast Guard plans to replace RACON,
with virtual Navigational marks through AIS.
Slide AIS 9

SAR
For coordinating marine SAR, it is important to
know the position and navigation status of ships in
the vicinity of the ship or person in distress.

AIS can provide such information without RT

communicaton which can be chaotic in a distress
situation.

The AIS standard has envisioned its use

on SAR Aircraft, and once fitted it will further help
in SAR management.

To aid SAR vessels and aircraft in locating people

in distress a standard for an AIS-SART is being
developed.
Slide AIS 10

How does AIS Work? - Principle of Operation

AIS consists of 1xVHF transmitter, 2xVHF TDMA
receivers, 1xVHF (DSC) receiver, and internal links to
ships Gyrocompass, GPS & ship’s log.

AIS transmitter automatically broadcasts information

about ships position, COG, SOG and CPA/TCPA at
regular intervals on two VHF Maritime Frequencies of
161.975 Mhz & 162.025 Mhz.

AIS gleans this data from ship’s GPS and Gyrocompass.

The AIS transmitter also transmits static information like

ships identity, IMO Number, her cargo, her destination etc
which is manually inputted during installation and at the
beginning of the voyage.

Ships in the vicinity with AIS transmit their own

information during their own time slots, which are so
allotted that there is never any interference between two
transmission.

This is achieved by using a patented STDMA technology

which does continuous synchronization of all AIS stations
in the area.
Slide AIS 11

STDMA technology

STDMA technique ensures that report from one AIS

station fits into one of 2250 time slots of 26.6 milliseconds
established every 60 seconds on each frequency.

Synchronization between all the AIS users in the area is

essential to avoid overlap of transmissions.

This needs some very accurate time management which is

provided by the GPS system.
Slide AIS 12

The AIS Display

When not transmitting, AIS receiver receive information

being transmitted by other ships and display them on the
AIS screen.

AIS Plot on a Ship

If the AIS is connected to ships radar or ECDISC, the

received information can also be shown on the PPI and
the electronic chart. This information can also be shown
if the IAa screen or chart plotter, showing the other
vessels' positions in much the same manner as a radar
display.
Slides AIS 13

Data Management in the AIS

Static Data (Has to be entered by ship staff)
 IMO Number (The vessel's Maritime Mobile Service Identity (MMSI) - a unique 9-
nine digit identification number.
 Call Sign (upto 7 digits) & Name (upto 20 characters)
 Length and Beam
 Type of Ship & Cargo
 Antenna Location on a ship

Data form Onboard Systems (Auto Updated from GPS/Gyro etc)

 Ships Position (in Lat & Long) with positional accuracy of

1/10,000th of a minute.
 Time In UTC accurate to nearest second when this data was

generated
 Course Over Ground (upto one decimal place accuracy)

 Speed Over Ground 0 to 102 knots

 Heading

 Rate of Turn (Where Fitted) right or left, 0 to 720 degrees per

minute
 CPA/TCPA

Voyage Related Data (To be entered by ship staff)

 Ships Draft (0.1 meter to 25.5 meters)

 Hazardous Cargo

 ETA (UTC) & Destination (Max. 20 characters)

 Route

Safety Related Messages (Entered By Ship Staff)

Slides AIS 14

Updating of Data
Dynamic
 At Anchor -- every 6 minutes
 Underway –

 0-14 kts -every 12 secs /4 secs when a/c

 14-23 kts - every 6 secs /2 secs when a/c

 >23 kts - every 3 secs /2secs when a/c

Static/Voyage Data –
Every 6 minutes or whenever amended

Safety Messages – As and when required.

Slides AIS 15

Advantages
 The system is fully automated with absolutely no
human intervention.
 Unlike Radar, It is not affected by rains or Sea.
 Its propagation is better than that of radar, due to
the longer wavelength.
 It’s possible to “see” around bends and behind
islands if the land masses are not too high.

Limitations
 The system coverage range is similar to other VHF
digital applications which depends upon the height of
the antenna. Typical Range 20 NM.
 With the help of repeater stations, the range can be
increased.
 Some vessels like fishing vessels leisure craft and
vessels below 500 grt may not be fitted with ais.
 Accuracy of the info recieved is only as accurate as
what is entered in the static/voyage or safety
messages data.
 The OOW should always be aware that AIS fitted on
other ships under certain circumstances, can be
switched off on the master's professional judgment.
Slides AIS 16
China and the AIS
Shore-based AIS network systems are now being built up around the
world. One of the biggest fully-operational, real time systems with full
routing capability is in China.

This system was built between the years 2003-2007. The entire coastline
of China is covered with approximately 250 base stations in hot-standby
configurations including 70 computer servers in three main regions.

Hundreds of shore based users, including 25 VTS centers, are connected

to the network and are able to see the maritime picture, but also to
communicate with the ship using SRM's (Safety Related Messages). All
data is in real time and will improve safety and security of ships and port
facilities.

On the internet, one can see real time disposition of ships in any part of
the world where such networks are fitted. Like the US coast, English
Channel, Japanese coast.
Slide AIS 17

A Representative AIS Picture of th British Channel.