Glossary of Terms used in Passage Planner
Term
Definition
The depth of the keel in metres at the aft end of the vessel.
Aft Draught
Air Draught
Air draught is the distance from the waterline to the highest point on a vessel.
This is used to calculate whether a vessel is able to proceed under an
overhead obstruction.
Block coefficient
A value that is published for the vessel that relates to the underwater shape
of its hull which directly affects the calculation of squat. Typical values range
from 0.6 – 0.9. This can be found within the onboard vessel particulars.
The width of the vessel in metres. This is required for squat calculations.
Breadth
Channel Width
The width of the channel that the vessel is navigating. The amount of squat
and the formula that is used depends on the width of the channel in relation
to the width of the vessel.
Charted clearance
The height in metres of an overhead obstruction, usually above Highest
Astronomical Tide. Obtained from the nautical chart or local information.
Charted depth
The depth in metres below chart datum, usually Lowest Astronomical Tide.
Obtained from the nautical chart or local information.
Charterer
The organisation that hires the vessel for the passage. This is an optional
information field for the cover page of the passage plan.
Default Charter speed
The speed in knots that the navigator wants to use as a default value for all
passage legs that have not been specified.
The depth of water allowing for charted depth and any tide.
Depth of water
The depth of the keel in metres at the forward end of the vessel.
Draught Forward
Dynamic UKC
The under keel clearance (UKC) of the vessel allowing for the depth of the
water and the effects of squat due to the vessel’s speed
End of Passage
The waypoint where a vessel ends the deep sea part of a voyage. Usually at
the arrival port where the vessel plans to transit from full speed to
manoeuvring status.
Estimated Time of Arrival.
ETA
Estimated Time of Departure.
ETD
Final course
Fix Frequency
The course that is planned to be steered when arriving at the waypoint at the
end of a great circle leg. Final course is calculated automatically by the
application.
Instruction to the bridge team regarding how frequently, usually in minutes,
that they should check the vessel’s position.
The nation state responsible for the oversight of the vessel.
Flag
The United Kingdom Hydrographic Office
Admiralty Way, Taunton, Somerset,
TA1 2DN, United Kingdom
www.admiralty.co.uk
See Draught Forward.
Forward Draught
Full away
The waypoint where a vessel commences the deep sea part of a voyage.
Usually on departing port where the vessel plans to transit from manoeuvring
status to full speed.
Great Circle (GC)
The shortest track on the earth’s surface between two way points. The vessel
may plan to follow a GC track on long ocean passages. Otherwise, a rhumb
line is generally the default.
Gross Tonnage
Optional field for the cover page of the passage plan. Gross Tonnage is
published in the vessel particulars on board.
Distance in metres from the keel to the highest point of a vessel.
Height of mast above keel
Height of tide
The height of the tide in metres obtained from published tables or software
applications.
IMO Number
The unique IMO ship identification number is an optional field for the cover
page of the passage plan obtained from the vessel particulars.
The course to be steered from a waypoint at the beginning of a new leg.
Initial course
The geographical position of the vessel north or south of the equator.
Latitude
A leg is planned route of the vessel between two waypoints.
Leg
A leg type may be rhumb line (RL) or great circle (GC).
Leg type
The maximum length of the vessel in metres.
Length overall
Linked tidal station
The station in ADMIRALTY TotalTide that is planned to be used at the
waypoint.
Loaded condition
Optional free text field for the cover page of the passage plan that can be
used to describe the amount of cargo on board.
The geographical position of the vessel east or west of Greenwich (0°)
Longitude
Mean (Draught)
Minimum OHC (Overhead
Clearance)
The midpoint in metres between the forward and aft draught. Calculated by
the application.
The minimum permitted distance in metres below an overhead obstruction as
specified by the vessel’s safety management system (SMS).
The minimum permitted overhead or under keel clearance in metres, usually
Minimum permitted clearance specified by the ship manager's safety management system (SMS).
Minimum UKC (Under Keel
Clearance)
MMSI
The minimum permitted distance in metres between the vessel’s keel and the
sea bed as specified by the vessel’s safety management system (SMS).
A Maritime Mobile Service Identity (MMSI) is a nine digit number which
uniquely identifies radio transmitting stations as per the vessel particulars.
Essentially this is the digital phone number of a vessel and is an optional
field for the cover page of the passage plan.
The United Kingdom Hydrographic Office
Admiralty Way, Taunton, Somerset,
TA1 2DN, United Kingdom
www.admiralty.co.uk
Optional free text field for the cover page of the passage plan.
Passage name
Planned Speed
The speed in knots between waypoints. The application calculates the speed
according to planned schedule but it can be overwritten by the navigator
when planning the passage. For new passages this is filled from the default
charter speed.
The port where the vessel is registered as per vessel particulars.
Port of Registry
Position fixing method
Instructions for the bridge team on how the vessel’s position should be fixed
at each stage of the passage. Abbreviated codes for each method can be set
up in the Watchkeeping menu.
Rhumb Line (RL)
The direct route between two waypoints and is represented on the chart
display as a straight line. This is the default leg type.
Sea and swell
The allowance in metres that takes account of the sea and swell conditions
that may reduce calculated clearances.
Sea Passage
The details of the deep sea passage between the full away and end of
passage waypoints. This is important because it governs the vessel
schedule as required by the charterer.
Ship’s time
The offset at each waypoint between local time used on board the vessel
and UTC (Universal Coordinated Time)
Squat
The decrease in metres of under keel clearance which occurs when a vessel
is moving through the water in a confined channel. Calculated by the
application.
The vessel’s draught in metres not allowing for any speed.
Static Draught
Summer Dead Weight
The carrying capacity of a vessel when loaded to its assigned summer load
line when floating in salt water. This optional field for the cover page of a
passage plan can be filled from the vessel particulars on board.
Summer load Draught
The maximum draught to which a vessel can load without submerging its
assigned summer load line. This optional field for the cover page of a
passage plan can be filled from the vessel particulars on board.
Trim
The difference in metres between the forward and aft draughts. This is
calculated by the application.
The planned radius of a turn at a waypoint.
Turn radius
Voyage Number
Waypoint
The number that is usually assigned on board to the whole voyage, which
may consist of a number of passages. This is an optional field for the cover
page of a passage plan.
A passage is made up of a series of geographical points which are known as
waypoints.
The United Kingdom Hydrographic Office
Admiralty Way, Taunton, Somerset,
TA1 2DN, United Kingdom
www.admiralty.co.uk