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Glossary
AIS
Universal Shipborne Automatic Identification System. A system of transceivers
installed on vessels which send continuously updated navigation information.
An AIS receiver or transceiver is used to monitor these transmissions and the
AIS
WatchMate
is used to display this information and trigger alarms when there
is a risk of collision.
BRG /
Bearing
The location of another vessel typically expressed as true or magnetic degrees.
May also be expressed as relative degrees from your vessel's heading.
Class A/B
There are two classes of AIS transceivers. Class A are used on vessels which
have mandatory requirements to carry AIS transceivers. Class B are used on
vessels for which AIS transceivers are optional.
COG
Course over ground. The course a vessel is making which is not necessarily
the same as the vessel's heading.
CPA
Closest point of approach. The nearest distance in nautical miles two vessels
will come to one another if they both maintain their current course and speed.
Filter
A set of criteria used to determine if a target should be included in the target
list, such as its range or speed.
GPS
Global Positioning System. Used to provide your vessel's current position,
course, and speed.
IMO
International Maritime Organization. A unique IMO number is permanently
assigned to each ship and may be used to find additional registration
information for a particular vessel.
HDG /
Heading
The course a vessel is steering.
MMSI
Maritime Mobile Service Identity. Used as a radio identifier for each vessel with
digital radios such as an AIS transceiver. Vessels may also transmit their name
to facilitate easier identification. These transmissions occur at a different
interval than position information and as a result the name may not be
immediately available. All AIS transceivers require a unique MMSI. The
AIS
WatchMate
will not transmit until you configure your MMSI.
Profile
A group of settings. Profiles allow you to organize filter and alarm settings and
activate them together when your navigation situation changes.
RNG /
Range
The distance in nautical miles between two vessels.
ROT
Rate of turn. The number of degrees a vessel is turning over a specified
amount of time. Usually per minute but may also be per 30 seconds.
SOG
Speed over ground. The actual speed in knots a vessel is making over the
ground.
Target
Another vessel for which AIS information has been received.
Target List
The set of all targets which meet the filter requirements.
TCPA
The time until the closest point of approach.
