This section should give a short
introduction to the limitations of a is
system and operator attention to
possible AIS limitations the officer of
the watch
oooww should always be aware that other
ships in particular leisure craft
fishing boats and warships and some
coastal shore stations including vessel
traffic service pts centers might not be
fitted with a is the officer on watch
should always be aware that other ships
fitted with a is as mandatory carriage
requirement might switch off a is under
certain circumstances by professional
judgment of the master switching off of
the AIS may make it more likely that the
ship will be checked out leading to
unnecessary inspections since pleasure
crafts and other small vessels are not
required to carry a is and the AIS may
be switched off or out of order on
vessels required to carry a is the
officer on watch must always be aware
that the traffic information provided by
AIS may not get a complete picture about
the situation around own ship the
officer on watch must always be aware
the transmission of erroneous
information entails a risk to other
ships as well as their own the users
remain responsible for all information
entered into the system as well as the
information added by the sensors
this means that the operator must check
the own ship a is information at regular
intervals and whenever he suspects that
something is amiss the accuracy of the
AIS information received is only as good
as the accuracy of the AIS information
transmitted that is the AIS information
presented on your display may vary in
quality
depending on the quality of the
information transmitted from each ship
the officer on watch should be aware
that poorly configured or calibrated
ship's sensors positions speed and
heading sensors might lead to incorrect
information being transmitted incorrect
information about one ship displayed on
the bridge of another ship could be
dangerously confusing if no sensor is
installed or if the sensor fails to
provide data the a is automatically
transmits the not available message
however the built-in integrity check
cannot validate the contents of the data
problem it would not be prudent for the
officer on watch to assume that the
information received from other ships is
of a comparable quality and accuracy to
that which might be available on own
ship the potential of a is as a
collision avoidance device is recognized
and AIS may be recommended as such a
device someday soon however great care
must be taken as a is may not give a
complete traffic overview or accurate
enough information about some or all of
the relevant targets when a is
information is used to assist in
collision avoidance decision-making the
following cautionary points should be
borne in mind a is is an additional
source of navigational information it
does not replace but supports
navigational systems such as radar arpa
and VTS the use of BTS does not negate
the responsibility of the officer on
watch to comply at all times with the
call rag the user should not rely on a
is as the sole information system but
should make use of all relevant safety
information
available the use of a is on board ship
is not intended to have any special
impact on the composition of the
navigational watch which would continue
to be determined in accordance with the
seafarers training certification and
watchkeeping code s TCW once a ship has
been detected a is can assist in
tracking it as a target by monitoring
the information broadcast by that target
its actions can also be monitored
changes in heading and course are for
example immediately apparent and many of
the problems common to tracking targets
by radar namely clutter targets wapis
ships pass close by and target loss
following a vast maneuver do not affect
kis kis can also assist in the
identification of targets by name call
sign and ship type and navigational
status VTS centers may send information
about vessels which are not carrying a
is and which are tracked only by VTS
radar via the AIS two vessels equipped
with a is particular care should always
be taken when using information that has
been related by a third-party accuracy
of these targets may not be as complete
is actual directly received targets VTS
centers may send short messages either
21 ship all ships or ships within a
certain range or in a special area such
as navigational warnings traffic
management information port management
information differential global
navigation satellite system corrections
may be sent by VTS via a is this can
increase the accuracy of the gps derived
data on ships within a
s range day is may be used in
search-and-rescue operations especially
in combined helicopter and surface
searches a is allows the direct
presentation of the position of the
vessel in distress on other displays
such as radar or ecs practice which
facilitates the task of search and
rescue SAR crafts for ships in distress
not equipped with a is the on-scene
coordinator osc could create a pseudo a
is target a is when fitted to selected
fixed and floating aids to navigation
can provide the following information to
the Mariner position status title and
current data whether and visibility
conditions AIS will play a role in an
overall international maritime
information system supporting voyage
planning and monitoring this will help
administration's to monitor all the
vessels in their areas of concern and to
track dangerous cargo after the sep
tember 11th events authorities in the US
and the EU envision an important role
for a is in the field of higher security
systems