Marine Abbreviation (A to D)



Always accessible and always afloat
Able-bodied seaman, certificated by examinations, who must have had at least three years service at sea. An unqualified seaman who has nine months sea service or more is called an Ordinary Seaman.
Stern or towards the stern of the ship.
Admiralty measured mile, 6,080 feet or 1,853.184 metres as distinguished from the nautical mile of 6,045.95 feet or 1,842.8055 metres. The mean nautical mile is 6,076.91 feet or 1,852.2421 metres.
Ad Valorem
Latin – according to the value. An Ad Valorem stamp on deeds or documents is one fixed in proportion to the amount of rent reserved or other element of value expressed in the deed.
Ad Valorem Freight
Freight paid in accordance with or in relation to the value of the merchandise shipped.
Advance Freight
(Freight paid in advance or freight pre-paid) – freight which is paid against the delivery or handing over of the original Bills of Lading. In most cases freight is due for payment on presentation of the Shipping Order.
Advance to Master
Money advanced by the Shipper to the Master of the ship to meet immediate disbursements at the loading port. It is treated as a loan recoverable from the shipowner.
A contract to carry goods by sea or air. charterparties and Bills of Lading are contracts of afreightment.
A tanker of 79,999 dwt, ie at the top of the range 45,000 to 79,999 dwt which is one of the ranges used in Average Freight Rate Assessment.
Near or towards the stern or rear of a vessel.
Aft Back-Spring
A mooring line running from the aft end of a vessel to a point on the quay some distance for’d of this, to prevent her from moving astern.
Aft Peak Tank
A tank positioned at the aft end of a ship often filled either with fresh water or sea water ballast.
Air Draft
The height of a ship taken from the summer load line to the top of the mast. This calculation is most important if the ship is meant to trade or navigate under bridges.
All Time Saved
The time saved by a vessel from the completion of loading/ discharging to the expiry of the laytime.
Always Accessible
(Reachable on arrival) – term in respect of the loading and/or discharging berth which must be accessible.
Always Afloat
(Always safely afloat) – a charterparty clause which stipulates that the ship is to berth for loading or discharging without touching the bottom of the sea/river/lake, etc.
Arrived Ship
In conjunction with a voyage charterparty a ship has “arrived” when she is within the usual waiting area of the port. Provided she is ready to load/discharge she can give Notice of readiness and laytime starts to run.
Always Afloat
Always Accessible Always Afloat
Always Afloat or Safe Aground. Condition for a vessel whilst in port
Amsterdam-Antwerp-Rotterdam Area
Toward the rear (stern) of the ship. Behind.
On or within the ship
On the deck (not over it – see ALOFT)
Address Commission
Additional chartering terms at the end of a charter party
Arrival First Sea Pilot Station (Norway)
The hiring of a ship in whole or part
At or towards the stern or rear of a ship
Touching or fast to the bottom
All Going Well
Australian Hold Ladders
Artificial objects to supplement natural landmarks indicating safe and unsafe waters
Above the deck of the ship
In or toward the centre of the ship
A place suitable for anchorage in relation to the wind, seas and bottom
Antwerp-Hamburg Range
Arrival Pilot Station
Amsterdam-Rotterdam–Antwerp-Gent Range
Method of settling disputes which is usually binding on parties. A clause usually in a charter party
American Shipbrokers Association
Any Safe Port in the World
In the back of the ship, opposite of ahead
Any Time Day/Night Sundays and Holidays Included
At right angles to the centreline of the ship
Actual Times Used to Count
See beam.
abnormal magnetic variation
Designation applied to any anamolous value of the magnetic variation of which the cause is unknown. cf local magnetic anomaly.
In the sense used in pilotage and ship handling means “near”. eg “To keep the E shore aboard”. “Close aboard” means “Very near”. cf borrow.
Uptide or upstream of a position.
A shoal, rock or other feature is termed above-water if it is visible at any state of the tide, cf awash, dries, below-water.
Steep: precipitous. cf bold.
abyssal or abysmal
Relating to the greatest depths of the ocean (literally, without bottom).
abyssal gap
A narrow break, in a ridge or rise, or separating two abyssal plains.
abyssal hills
A tract of small elevations on the sea floor.
abyssal plain
A flat, gently sloping or nearly level region at abyssal depths.
accretion or deposition
The depositing of material on the bottom or the coast by water movement; the opposite to erosion (qv).
When altering course, the distance that the compass platform of a ship has advanced in the direction of the original course on completion of a turn (the steadying point). It is measured from the point where the wheel was put over.
aeronautical radiobeacon
A radiobeacon primarily for the use of aircraft. Usually abbreviated to “aero radiobeacon”
A tributary river or brook.
Floating, as opposed to being aground.
age of the Moon
The interval in days and decimals of a day since the last New Moon.
age of the tide
Old term for the lag between the time of new or full Moon and the time of maximum spring tidal range.
See double tide.
agonic line
A line joining points on the Earth’s surface where there is no magnetic variation.
Resting on the bottom.
A ship is alongside when side by side with a wharf, wall, jetty, or another ship.
A point in the sea where the tide has no amplitude. Co-tidal lines radiate from an amphidromic point and co-range lines encircle it.
Water area which is suitable and of depth neither too deep nor too shallow, nor in a situation too exposed, for vessels to ride in safety. An area set apart for vessels to anchor, such as: examination anchorage. One used by ships while awaiting examination. quarantine anchorage. A special anchorage set aside, in many ports, for ships in quarantine. safety fairway anchorage. An anchorage adjacent to a shipping safety fairway (qv).
anchor buoy
Small buoy occasionally used to mark the position of the anchor when on the bottom; usually painted green (starboard) or red port), and secured to the crown of the anchor by a buoy rope.
angle of cut
The lesser angle between two position lines.
The point in the orbit of a planet which is farthest from the Sun. cf perihelion.
The point in the orbit of the Moon which is farthest from the Earth. cf perigee.
The waterways that give access or passage to harbours, channels, etc.
The portion of a wharf or quay lying between the waterside edge and the sheds, railway lines or road.
Geologically, a covered passage cut through a small headland by wave action.
archipelagic apron
A gentle slope with a generally smooth surface on the sea floor, particularly found around groups of islands or seamounts.
arc of visibility
The sector, or sectors, in which a light is visible from seaward.
area to be avoided
A routeing measure comprising an area within defined limits in which either navigation is particularly hazardous or it is exceptionally important to avoid casualties and which should be avoided by all ships, or certain classes of ship.
arm (of a jetty, etc)
A narrow portion projecting from the main body.
arm of the sea
A comparatively narrow branch or offshoot from a body of the sea.
arming the lead
Placing tallow in the recess in the bottom of the sounding lead to ascertain the nature of the bottom.
articulated loading platform or column (ALP) or (ALC)
Is a development of the SALM with the anchor span and buoyant frame or tube replaced by a metal lattice tower, buoyant at one end attached at the other by a universal joint to a concrete-filled base on the seabed. Some are surmounted by a platform which may carry a helicopter deck and a turntable with reels for lifting hawsers and hoses clear of the water, and have emergency accommodation. These are termed Articulated Loading Platforms (ALPs). In bad weather, a tower may be inclined at angles up to 20° to the vertical.
artificial harbour
A harbour where the desired protection from wind and sea is obtained from moles, jetties, breakwaters, etc. (The breakwater may have been constructed by sinking concrete barges, vessels, etc, to form a temporary shelter.)
artificial horizon
A horizon produced by bubble, gyro or mercury trough to allow measurement of altitude of celestial bodies.
astronomical arguments
See Admiralty Tide Tables.
astronomical twilight
The period between the end of nautical twilight (qv) and the time when the Sun’s centre is 18° below the horizon in the evening, and the period of the time when the Sun’s centre is 18° below the horizon in the morning and the beginning of nautical twilight in the morning.
A ring-shaped coral reef which has islands or islets on it, the shallow rim enclosing a deeper natural area or lagoon; often springing from oceanic depths.
A small atoll on the margin of a larger one.
A shoal, rock or other feature is termed awash when its highest part is within 0.1 m, or with fathoms charts within 1 foot, of chart datum (qv). awash at high water. May be just visible at MHWS or MHHW. cf dries, above-water.


Bale Capacity
The cubic capacity of the cargo space in the holds of a vessel while allowing for broken stowage.
Bare Boat Charter
An agreement under which the charterers hire or charter the ship for a long period, appoint the Master and crew and pay all running expenses. During the hire period the charterers maintain the ship.
Registered breadth of a ship measured from the outside of the hull amidships, ie the greatest width of a vessel.
Berth Charterparty
A voyage charter whereby the ship is chartered to load at a berth.
Term for the Baltic International Freight Futures & Market which offers shipowners, operations and charterers protection against the risks of volatile freight rates by means of a standardised contract settled against an index of international dry bulk voyages.
Where a seller/shipper issues a ‘letter of indemnity’ in favour of the carrier in exchange for a clean bill of lading
Bunker Adjustment Factor. A Fuel Surcharge expressed as a percentage added or subtracted from the freight amount, reflecting the movement in the market place price for bunkers.
Cubic capacity of a vessels holds to carry packaged dry cargo such as bales/pallets
Heavy weight, often sea water, necessary for the stability and safety of a ship which is not carrying cargo
Compensation for relatively long ballast voyage
Bareboat Charter – Owners lease a specific ship and control its technical management and commercial operations only. Charterers take over all responsibility for the operation of the vessel and expenses for the duration.
Before Breaking Bulk. Refers to freight payments that must be received before discharge of a vessel commences
Both Dates Inclusive
The maximum breadth or the greatest width of a ship
Beneath the deck
Both Ends (Load & Discharge Ports)
Both Inclusive
The Baltic and International Maritime Council
(Bill of Lading) A document signed by the carrier which acts as a Contract of Affreightment, a receipt and evidence of title to the cargo.
Booking Note
Bunker on Board
Best Offer
The forward part of a ship
Bunkers Remaining on Board
Percentage of freight payable to broker (by owners in c/p’s) or applicable to sale or purchase
BSS 1/1
Basis 1 Port to 1 Port
Berth Terms
A vertical partition separating compartments
This is the assembly of pieces of cargo, secured into one manageable unit. This is relevant to items such as Structural Steel, Handrails, Stairways etc. Whilst this is a very flexible description, a rule of thumb is to present cargo at a size easily handled by a large (20 tonne) fork lift.
Name given for vessels Fuel and Diesel Oil supplies (Originates from coal bunkers)
An anchored float used for marking a position on the water or a hazard or a shoal and for mooring
Brackish Water Arrival Draft
The wind is said to back when it changes direction anticlockwise.
That part of the shore whose seaward limit is the waterline of MHWS and whose landward limit is the extreme limit of wave action (such as occurs in onshore gales at equinoctial spring tides (qv).
Waves reflected from obstructions such as cliffs, seawalls, breakwaters, etc, running seaward and combining with the incoming waves to cause a steep and confused sea.
backwash marks
Small scale oblique reticulate pattern sometimes produced by the return swash of the waves on a sandy beach. cf ripple marks, beach cusps.
An arm of the sea, usually lying parallel with the coast behind a narrow strip of land, or an arm of a river out of the main channel, and out of the main tidal stream or current.
Oceanographically, an area of positive relief over which the depth of water is relatively shallow, but normally sufficient for safe surface navigation. The term should not be used for features rising from the deep ocean. Also, the margin of a watercourse, river, lake, canal, etc. The right bank of a river is the one on the right hand when facing downstream.
A bank of sand, mud, gravel or shingle, etc near the mouth of a river or at the approach to a harbour, causing an obstruction to entry.
bar buoy
A buoy indicating the position of a bar.
An obstruction, usually artificial, in a river. eg Thames Barrier.
barrier reef
A coral reef, lying roughly parallel with the shore, but separated from it by a channel or lagoon. The distance offshore may vary from a few metres to several miles.
Dark green or brown igneous rock, often in columnar strata.
An almost land-locked area leading off an inlet, firth or sound. Also, an area of water limited in extent and nearly enclosed by structures alongside which vessels can lie. Oceanographically, a depression more or less equidimensional in form, and of variable extent. Tidal basin:. A basin without caisson or gates in which the level of water rises and falls with the tide. Sometimes called an open basin. Non-tidal basin: A basin closed by a caisson or gates to shut it off from open water, so that a constant level of water can be maintained in it. Also called a wet dock. Impounding basin: A basin in which water can be held at a certain level, either to keep craft afloat or to provide water for sluicing. Turning Basin: An area of water or enlargement of a channel in a port, where vessels are enabled to turn, and which is kept clear of buoys, etc for that purpose.
The science of the measurement of marine depths. Submarine relief.
A comparatively gradual indentation in the coastline, the seaward opening of which is usually wider than the penetration into the land, cf bight, gulf.
Term used in Florida for a small bay, and in Mississippi and Louisiana for a waterway through lowlands or swamps, connecting other bodies of water, and usually tidal or with an imperceptible current.
Any part of the shore where mud, sand, shingle, pebbles, etc, accumulate in a more or less continuous sheet. The term is not used to describe areas of jagged reef, rocks or coral. to beach: To run a vessel or boat ashore. To haul a boat up on a beach.
beach cusps
Triangular ridges, or accumulations, of sand or other detritus regularly spaced along the shore, the apex of the triangle pointing towards the water, giving a serrated form to the water-edge.
beach ridges
The seaward boundaries of successive positions of beaches on seaward-advancing shores. The intervening depressions may be extensive and contain a lagoon, marsh, mangrove swamp, etc, or be narrow and consist of sand, cf storm beach.
A fixed artificial navigational mark, sometimes called a daybeacon in the USA and Canada. It can be recognised by means of its shape, colour, pattern or topmark. It may carry a light, radar reflector or other navigational aid.
beacon tower
A major masonry beacon the structure of which is as distinctive as the topmark.
beam: on the
An object is said to be on the beam, or abeam, if its bearing is approximately 90° from the ship’s head.
beam sea
The condition where the sea and swell approach the ship at approximately 90° from the ship’s head.
anchor bearing: The bearing of a shore object from the position of the anchor. check bearing: The bearing of an extra object taken to check the accuracy of a fix. clearing bearing: The bearing of an object, usually taken -from a chart, to indicate whether a ship is clear of danger. line of bearing: A ship runs on a line of bearing if she makes good a ground track on a constant bearing of an object.
The bottom of the ocean, sea, lake or river. Usually qualified, eg seabed, river bed.
A buoy fitted with a bell which may be actuated automatically or by wave motion.
A shoal, rock or other feature is termed below-water or underwater if it is not visible at any state of the tide. cf above-water.
See terrace.
A mark, which may consist of an arrow cut in masonry, a bolthead or a rivet fixed in concrete, etc, whose height, relative to some particular datum is exactly known. (See Admiralty Tidal Handbook No 2.)
An horizontal ledge on the side of an embankment or cutting to intercept falling earth or to add strength. Also, a narrow, nearly horizontal shelf or ledge above the foreshore built of material thrown up by storm waves. The seaward margin is the crest of the berm.
The space assigned to or taken up by a vessel when anchored or when lying alongside a wharf, jetty, etc. to give a wide berth. To keep well away from another ship or any feature.
A crescent-shaped indentation in the coastline, usually of large extent and not more than a 90° sector of a circle. cf bay, gulf.
bilge (or keel) blocks
A row of wooden blocks on which the bilges (or keel) of a ship rest when she is in dock or on a slipway.
A narrow promontory.
Very wet mud, a feature of estuaries and rivers; of a dangerous nature such that a weight will at once sink into it.
blind rollers
When a swell wave encounters shoal water it is slowed and becomes steeper. If the depth or extent of the shoal or rock is sufficient to cause the wave to steepen markedly but not to break, the resulting wave is termed a blind roller.
A headland or short stretch of cliff with a broad perpendicular face. As adjective: Having a broad perpendicular or nearly perpendicular face.
boat camber
See camber.
boat harbour
An area of sheltered water in a harbour set aside for the use of boats, usually with moorings, buoys, etc.
boat house
A shed at the water’s edge or above a slipway for housing a boat or boats.
boat pound
See pound.
boat slip
A slipway designed specifically for boats.
boat yard
A boat-building establishment.
Wet spongy ground consisting of decaying vegetation, which retains stagnant water, too soft to bear the weight of any heavy body. An extreme case of swamp or morass.
Rising steeply from deep water. Well-marked. Clear cut, cf abrupt.
Synonymous with steep-to.
A post (usually steel or reinforced concrete) firmly embedded in or secured on a wharf, jetty, etc, for mooring vessels by means of wires or ropes extending from the vessel and secured to the post. A very small bollard for the use of barges and harbour craft may be called a “dollie”.
A floating barrier of timber used to protect a river or harbour mouth or to enclose a boat harbour or timber pound. Also, a barrier of hawsers and nets supported by buoys used in the defence of a port or anchorage.
booming ground
A term used mainly in Canadian waters, and similar to timber pound (qv) where logs are temporarily held and stored for making up into rafts. The area is usually enclosed by a boom to retain the logs.
A tidal wave which propagates as a solitary wave with a steep leading edge up certain rivers. Formation is most apparent in wedge-shaped shoaling estuaries at times of spring tides. See Admiralty Manual of Tides.
In the sense used in pilotage means “keep towards, but not too near”, eg “To borrow on the E side of the channel”, cf aboard.
bottom, nature of the
The material of which the seabed is formed, eg mud, stones.
Water-rounded stones more than 256 mm in size, ie larger than a man’s head, cf cobbles.
Water in which salinity values range from approximately 0.50 to 17.00.
Waves or swell which have become so steep, either on reaching shoal water or on encountering a contrary current or by the action of wind, that the crest falls over and breaks into foam.
breaking sea
The partial collapse of the crests of waves, less complete than in the case of breakers, but from the same cause; also known as White Horses.
A solid structure, such as a wall or mole, to break the force of the waves, sometimes detached from the shore, protecting a harbour or anchorage. Vessels usually cannot lie alongside a breakwater.
A narrow ridge of rock, sand or shingle, across the bottom of a channel so as to constitute a shoal or shallow. Structure carrying road etc across waterway, road ravine etc. Movable bridges are usually swing bridges, or lifting or bascule bridges. Swing bridges may pivot about a point, either in mid-channel or on one bank. Bascule bridges may be single or double, depending on whether they lift from one or both banks.
An island which is connected to the mainland, or to a larger island, at low water, or at certain states of the tide, by a narrow ridge of rock, sand, shingle, etc.
broach to
To slew around inadvertently broadside on to the sea, when running before it.
broadside on
Beam on (eg to wind or sea).
broken water
A general term for a turbulent and breaking sea in contrast to comparatively smooth and unbroken water in the vicinity.
A small stream.
An arrangement of wooden planking to give passage between ship and shore when the ship is alongside. Also called a “gangway”.
building slip
A space in a shipbuilding yard where foundations for launching ways and keel blocks exist and which is occupied by a ship when being built.
A floating, and moored, artificial navigation mark. It can be recognised by means of its shape, colour, pattern, topmark or light character, or a combination of these. It may carry various additional aids to navigation. Cf lanby, light-buoy.
buoyant beacon
A floating mark coupled to a sinker either directly or by a cable that is held in tension by the buoyancy of the mark. Its appearance above the water generally resembles a beacon rather than a buoy; it does not rise and fall with the tide; and it normally remains in a vertical or near-vertical position. Formerly known as a Pivoted Beacon.


Carriers Lien
The shipowner’s right to withhold cargo from delivery to the consignee as security against the collection of freight and other charges for the shipment.
Charterers Option which may refer to the loading of a percentage of cargo more or less.
Oil that remains clinging to the sides and other parts of the tanks in an oil tanker following discharge.
A narrow compartment between two bulkheads extending across a ship, usually to separate oil tanks from machinery spaces in case of leaks.
Conditions of Class
Requirements which have to be attended to by the shipowner on the orders of the Classification Society before the vessel is confirmed as “class maintained”.
The receiver of the merchandise.
Consignment Note
A shipping document similar to a Bill of Lading supplied by the carrier for goods carried from one place to another. It contains particulars of freight payment and conditions. On delivery of the goods to the vessel this note is presented to the carrier for endorsement and is a proof of receipt of the goods onboard. It is not a document of title.
The sender or the shipper of the goods.
Cost and Freight
Means the price of the goods includes the cost and freight. Insurance, if any, is for the account of the consignee or receiver. (C&F or CNF).
Cost, Insurance and Freight
Commonly used in export and import work. The manufacturers, merchants or shippers, when quoting to the buyers include the cost of the item together with insurance and freight up to the point of destination. Unloading expenses are to be borne by the consignees or receivers. (CIF or CFI).
Currency Adjustment Factor
Cubic Metres
Cubic Feet
CFR (or C&F)
Cost and Freight
A map used by navigators
Charterers Option
Cost, Insurance & Freight. Seller pays all these costs to a nominated port or place of discharge.
Completely knocked down
Contract of Affreightment – Owners agree to accept a cost per revenue tonne for cargo carried on a specific number of voyages.
Carriage and Insurance paid to…
Contract of Affreightment Charter Party
Closing of Business
Closing of Business London
Cash On Delivery
Carriage of Goods by Sea Act
Port/berth delays
CONSIGNEE. Name of agent, company or person receiving consignment
Custom Of Port
CP (or C/P)
Charter Party
Charterers Pay Dues
Carriage Paid To
Customary Quick Despatch
Current Rate
Cargo Remaining on Board
Cargo Retention Clauses, introduced by charterers based on shortage of delivered cargo because of increased oil prices
Container Fitted
A nautical unit of measurement, being one tenth of a sea mile. See mile. Also, a term often used to refer to the chain cable by which a vessel is secured to her anchor. Also used to refer to submarine, or overhead, power or telephone cables.
cable buoy
A buoy marking the end of a submarine cable on which a cable ship is working. Also used in the sense of a telegraph buoy (qv).
A mound of rough stones or concrete of pyramidal or beehive shape used as a landmark.
A structure used to close the entrance to dry docks, locks and non-tidal basins. They are of two kinds; floating caissons which are detachable from the entrance they close, and sliding caissons which slid into a recess at the side of the dock, cf cofferdam. There are also dry docks which are closed by raising a flap-type door, hinged at the outer side of the dock sill.
Formed of, or containing, carbonate of lime or limestone.
calling-in point
See reporting point.
The breaking away of rock, stones, earth, etc from the face of a cliff.
A small basin usually with a narrow entrance, generally situated inside a harbour, eg Boat camber: a small basin for the exclusive use of boats.
A tank filled with water and placed against the hull of a stranded or sunken vessel. It is well secured to the vessel and then pumped out, the buoyancy thus added helping to lift the vessel.
can buoy
A nearly cylindrical buoy moored so that a flat end is uppermost.
A channel dredged or cut through dry land or through drying shoals or banks and used as a waterway. cf ship canal.
canal port
A port so situated that the waterway is entirely artificial.
A deep gorge or ravine with steep sides, at the bottom of which a river flows. Oceanographically, a relatively narrow, deep depression with steep sides, the bottom of which slopes continuously downwards.
A piece of land, or point, facing the open sea and projecting into it beyond the adjacent coast.
cargo transfer area
See transhipment area.
To turn a ship to a desired direction without gaining headway or sternway.
A floating stage or raft used in shipyards, for working from, and sometimes used as a fender between ship and wharf, etc. Also, a type of twin-hulled yacht. (The name is taken from various native-built craft common in the East Indies and some other parts of the world.)
catenary anchor leg mooring (CALM)
Incorporate a large buoy which remains on the surface at all times and is moored by 4 or more anchors which may lie up to 400 m from the buoy. Mooring hawsers and cargo hoses lead from a turntable on the top of the buoy, so that the buoy does not turn as the ship swings to wind and stream.
A narrow footway forming a bridge, eg connecting a mooring dolphin to a pierhead. Also known as a walkway.
A raised roadway of solid structure built across low or wet ground or across a stretch of water.
A small insular feature usually with scant vegetation; usually of sand or coral. Often applied to smaller coral shoals. cf islet.
centreline controlling depth
See controlling depths.
A comparatively deep waterway, natural or dredged, through a river, harbour, strait, etc, or a navigable route through shoals, which affords the best and safest passage for vessels or boats. The name given to certain wide straits or arms of the sea, eg English Channel, Bristol Channel. Oceanographically, a river valley-like elongated depression in ocean basins, commonly found in fans (qv).
character or characteristic of a light
The distinctive rhythm and colour, or colours, of a light signal that provide the identification or message, See Admiralty List of Lights.
chart datum
A level so low that the tide will not frequently fall below it. In the United Kingdom, this level is normally approximately the level of Lowest Astronomical Tide. It is the level below which soundings are given on Admiralty charts, and above which are given the drying heights of features which are periodically covered and uncovered by the tide. Chart datum is also the level to which tidal levels and predictions are referred in Admiralty Tide Tables. Chart datum is defined simply in the Glossary as the lever below which soundings are given on Admiralty charts. Chart datums used for earlier surveys were based on arbitrary low water levels of various kinds. Modern Admiralty surveys use as chart datum a level as close as possible to Lowest Astronomical Tide (LAT), which is the lowest predictable tide under average meteorological conditions. This is to conform to an IHO resolution which states that chart datum should be a level so low that the tide will not frequently fall below it. The actual levels of LAT for Standard Ports are listed in Admiralty Tide Tables. On larger scale charts abbreviated details showing the connection between chart datum and local land levelling datum are given in the tidal panel for the use of surveyors and engineers.
See dock sill.
Fragments formed when magma is blown into the air; larger in size than volcanic ash.
circular radiobeacon
A radiobeacon which transmits the same signal in all directions.
civil twilight
The periods of the day between the time when the Sun’s centre is 6° below the horizon and Sunrise (morning twilight), or between sunset and the time when the Sun’s centre is 6° below the horizon (evening twilight).
claw off
To beat or reach to windward away from a lee shore.
A stiff tenacious sediment having a preponderance of grains with diameters of less than 0.004 mm. It is impossible to differentiate between clay and silt by eye, but a sample of wet clay, when dried in the palm of the hand, will not rub off when the hands are rubbed together.
Applied to the bottom of the sea, harbour or river, means free from rocks or obstructions. cf foul.
clearing bearing
See bearing.
clearing marks
Selected marks, natural or otherwise, which in transit clear a danger or which mark the boundary between safe and dangerous areas for navigation.
Land projecting nearly vertically from the water or from surrounding land, and varying from an inconspicuous slope at the margin of a low coastal plain to a high vertical feature at the seaward edge of high ground. Can be formed by a fault in geological strata (inland).
(verb). To approach near.
close aboard
Very near
The meeting of the land and sea considered as the boundary of the land. cf shore. Also, the narrow strip immediately landward of the waterline of MHWS, or sometimes a much broader zone extending some distance inland.
coastal plain
A strip of flat consolidated land varying in width which may occur immediately landward of the coastline.
coastal waters
The sea in the vicinity of the coast (within which the coasting trade is carried out).
Navigating from headland to headland in sight of land, or sufficiently often in sight of land to fix the position of the ship by land features.
The strip of land with a somewhat indeterminate inner limit, immediately landward of the coastline. It may include such features as sand dunes, saltings, etc, which are associated with proximity to the sea, and merges into the hinterland where the features cease.
The landward limit of the beach. The extreme limit of direct wave action (such as occurs in onshore gales during Equinoctial Spring Tides. cf backshore. It may be some distance above the waterline of Mean High Water Springs, but for practical hydrographic purposes the two are usually regarded as coincident. Also, a general term used in describing the shore or coast as viewed from seaward, eg a low coastline.
coast radio station
See radio stations.
(adjective and adverb). Near to the coast, eg Coastwise traffic is that which sails round the coast, and to sail coastwise means coasting as opposed to keeping out to sea.
Water-rounded stones of from 64 mm to 256 mm in size, ie from the diameter of a man’s clenched fist when viewed sideways to slightly larger than the size of a man’s head. cf pebbles, boulders.
cocked hat
The triangle sometimes formed by the intersection of three lines of bearing on the chart. cf cut.
Watertight screen on enclosure used in laying foundations underwater; sometimes called a caisson.
Steep, long swell waves with high breaking crests.
See fan.
confused sea
The disorderly sea in a race; also when waves from different directions meet, due normally to a sudden shift in the direction of the wind.
conformal projection
Another name for orthomorphic projection (qv).
conical buoy
A cone-shaped buoy moored to float point up, cf can buoy, nun buoy.
conspicuous object
A natural or artificial mark which is outstanding, easily identifiable, and clearly visible to the mariner over a large area of sea in varying conditions of light. If the scale is large enough they will normally be shown on charts in bold capitals, or on older charts by the note ‘conspic‘. cf prominent.
constants (harmonic)
The phase-lag (g) and the amplitude (H) of a constituent of the tide.
constants (non-harmonic)
The average time and height difference of high and low water, referred to the times and heights at a standard port; the time can also be referred to the time of Moon’s transit.
constituent (of the tide)
The tidal curve can be considered as being composed of a number of cosine curves, having different speeds, phase-lags and amplitudes, the speed being determined from astronomical theory and the phase-lags and amplitudes being determined from observation and analysis. These cosine curves are known as constituents of the tide. See Admiralty Tidal Handbooks No 1.
A rigid, non-disposable, cargo-carrying unit, with or without wheels. Standard lengths are: 6.1 m (Twenty-foot Equivalent Unit (teu)) and 12.2 m (Forty-foot Equivalent Unit (feu)): both width and height are standardised at 2.44 m.
The main types of container are:
collapsible: Can be stowed when not in use;
dry bulk: For cargoes such as dry chemicals or grain;
dry cargo: For general cargo;
flat rack: For timber, large items or machinery;
refrigerated: Insulated and usually fitted with its own refrigeration systems.
container terminal
A specially equipped berth with storage area, where standard cargo containers are loaded or unloaded.
continental borderland
A province adjacent to a continent, normally occupied by or bordering a continental shelf, that is highly irregular, with depths well in excess of those typical of a continental shelf.
continental margin
The zone, generally consisting of the shelf, slope and rise, separating the continent from the deep sea bottom.
continental rise
A gentle slope rising from the oceanic depths towards the foot of the continental slope.
continental shelf
A zone adjacent to a continent (or around an island) and extending from the low water line to a depth at which there is usually a marked increase of slope towards oceanic depths. Conventionally, its edge is taken as 200 m, but it may be between about 100 m and 350 m.
continental slope
The slope seaward from the shelf edge to the beginning of a continental rise or the point where there is a general reduction in slope.
A line joining points of the same height above or depths below, the datum, cf fathom line.
controlling depth
Depths in a channel are designated as follows:
controlling depth. The least depth within the limits of a channel: it restricts the safe use of the channel to draughts of less than that depth.
centreline controlling depth. A depth which applies only to the channel centreline: lesser depths may exist in the remainder of the channel.
mid-channel controlling depth. A depth which applies only to the middle half of the channel.
The boundary or region where two converging currents meets, with the result that the water of the current of higher density sinks below the surface and spreads out at a depth which depends on its density.
Belt of buckets or similar contrivance for transporting cargo, especially ores or coal, from ship to shore or vice versa.
The top course of masonry in a wall: the waterside top edge of a wall.
Hard calcareous substance secreted by many species of marine polyps for support, habitation, etc. It may be found either dead or alive. Although depths over many coral reefs have remained unchanged for 50 years or more, coral growth and the movement of coral debris can change depths over reefs and in channels significantly. At depths near the surface, coral growth and erosion are nearly balanced. At greater depths the growth increases, with the most rapid growth occurring in depths of more than 5 m. The greatest rate of growth of live coral is attained by branching coral and is a little over 0.1 m a year, but this type of coral would probably not damage a well-built vessel. The rate of growth of massive coral reefs which could damage even the largest vessel is about 0.05 m a year. The continual erosion of coral reefs causes the formation of coral sands and shingles which may be deposited and cause fluctuations in the depths on reefs or in the channels between them. Windward channels tend to become blocked by this debris and by the inward growth of the reefs, but leeward channels tend to be kept clear by the ebb tide, and deposits the debris in deep water outside the reefs. The greatest recorded decrease in depths over coral reefs due to be combined growth of coral and deposit of debris is 0.3 m a year. Decrease in depths due only to the deposition of coral debris can be more rapid and is more difficult to assess.
coral island
An island principally or entirely formed of coral. It may be one of three kinds: an elevated coral reef forming an island; a reef island formed by the accumulation of coral debris on a submerged fringing or barrier reef; or an atoll.
coral reef
Reefs, often of large extent, composed chiefly of coral and its derivatives. See atoll, barrier reef, fringing reef.
co-range lines
Lines on a tidal chart joining points which have the same tidal range or amplitude; also called co-amplitude lines. Usually drawn for a particular tidal constitutent or tidal condition (eg mean spring tides).
An entire mountain province, including all the subordinate ranges and groups and the interior plateaux and basins.
coriolis force
An apparent force acting on a body in motion, due to the rotation of the Earth, causing deflection (eg of winds and currents), to the right in the N hemisphere and to the left in the S hemisphere.
co-tidal chart
A chart combining co-range lines with co-tidal lines; co-tidal charts may refer to the tide as a whole or to one or more tidal constituents.
co-tidal lines
Lines joining points at which high water (or low water) occurs simultaneously. The times may be expressed as differences from times at a standard port or as intervals after the time of Moon’s transit.
The intended direction of the ship’s head.
course made good
The resultant horizontal direction of actual travel. The direction of a point of arrival from a point of departure.
A small indentation in a coast (usually a cliffy one), frequently with a restricted entrance and often circular or semi-circular in shape.
A carriage of wood or metal in which a vessel sits on a slipway.
A term applied to small vessels and boats. harbour craft. Boats, barges, lighters, etc, used on harbour work. a handy craft. An easily manoeuvred boat.
A mechanical contrivance for lifting weights. The main types are:
cargo crane. For transferring cargo between a ship’s hold and the shore or lighter;
container crane. specifically intended for handling containers;
fixed crane. Built on the shore for use in one place only;
floating crane. mounted on a lighter or pontoon, cf crane lighter;
gantry crane. Mounted on a frame or structure spanning an intervening space. cf Transporter;
luffing crane. Can move a load nearer or farther from the base of the crane by raising or lowering the jib;
mobile or crawler crane. Self-propelled on wheels or caterpillar tracks;
portal crane. A type of gantry crane with vertical legs giving sufficient height and width for vehicles or railway trucks to pass between them;
wharf crane. Located on a wharf or pier specifically for serving vessels alongside it.
Cranes are normally described by their lifting capacity, eg a 15-tonne crane.
crane lighter
A lighter especially fitted with a crane. May be self-propelled or towed.
A bowl-shaped cavity; in particular, at the summit or on the side of a volcano.
A comparatively narrow inlet, of fresh or salt water, which is tidal throughout its course.
Of a hill, the head, summit or top: of a mountain range, the line joining the highest points. Similarly, of an elevation of the seabed, or of a swell or wave.
A wave formation imposed across the prevailing waves. cf confused sea.
Similar to cross-sea but the waves are longer swell waves.
A tunnelled drain or means of conveying water beneath a canal, railway embankment or road (sometimes the size of a small bridge, ie up to about 3 m across). Also, a channel for electric cables.
The non-tidal horizontal movement of the sea which may be in the upper, lower or in all layers. In some areas this movement may be nearly constant in rate and direction while in others it may vary seasonally or fluctuate with changes in meteorological conditions. The term is often used improperly to denote tidal streams. Currents flow at all depths in the oceans, but in general the stronger currents occur in an upper layer which is shallow in comparison with the general depths of the oceans. Ocean current circulation takes place in three dimensions. A current at any depth in the ocean may have a vertical component, as well as horizontal ones; a surface current can only have horizontal components. The navigator is primarily interested in the surface currents.
Current diagrams
use arrows to indicate predominant direction, average rate and constancy, which are defined as follows:
Predominant direction. The mean direction within a continuous 90° sector containing the highest proportion of observations from all sectors.
Average rate. The rate to the nearest 1/4 kn of the highest 50% in predominant sectors as indicated by the figures on the diagrams. It is emphasised that rates above or below those shown may be experienced.
Constancy. The thickness of the arrows is a measure of its persistence; eg low constancy implies marked variability in rate and particularly direction.
The intersection on the chart of two or more position lines. An opening in an elevation or channel. Similar to a canal but shorter. May constitute a straightening of a bend in a winding channel.
cut tide
A tide which fails to reach its predicted height at high water.


Space booked by a broker or charterer to load cargo on a ship which for some reason or other it is not used. Although the booked space is unused freight, it will still have to be paid.
The total weight which a ship can carry, including cargo, provisions, fuel, stores, bunkers, crew and spares up to her Plimsol Line or marks. (Alternatively, the difference between light and loaded displacements.)
Deadweight Cargo Capacity
This refers to the actual capacity of the deadweight cargo the ship is able to carry. Often referred to as Cargo Carrying Capacity or Cargo Deadweight.
Daily compensation paid by the charterer to the Owner of a ship for delays in loading and discharging beyond the time agreed in the charterparty (laydays).
Despatch Days
In a Voyage charterparty these are days saved while loading and/or discharging compared to the time specified in the contract. On such occasions the charterers are compensated by a remuneration (despatch) which is normally half of the demurrage rate.
Claim by the Owner of a ship as unliquidated damages against the charterers once the period of demurrage has expired.
Disponent Owner
The person or company who controls the commercial operation of a ship, responsible for deciding the ports of call and the cargoes to be carried. Typically a time charterer.
Disbursement Account
Deliver At Frontier
Days all Purposes (Total days for loading & discharging)
Damages for Detention. Penalty if cargo is not ready when ship arrives for working (1st day of Laycan). This is not detention which is charged for ships time on delay. If the cargo is ready there is no DAMFORDET.
Delivered Duty unpaid.
Delivered Duty Paid.
A permanent covering over a compartment, hull or any part thereof
Demurrage (Quay Rent). Money paid by the shipper for the occupying port space beyond a specified “Free Time” period.
Delivered Ex Quay
Delivered Ex Ship
Despatch. Time saved, reward for quick turnaround- in dry cargo only
Detention (See DAMFORDET)
Deviation. Vessel departure from specified voyage course
Deadfreight. Space booked by shipper or charterer on a vessel but not used
Despatch Half Demurrage on All Time Saved Both Ends
Despatch Half Demurrage on Working Time Saved Both Ends
Dropping Last Outwards Sea Pilot (Norway)
Diesel Oil
Dropping Off Last Sea Pilot (Norway)
Dropping Outward Pilot
Department of Transport
Discountless and Non-Returnable Cargo and/or Ship Lost or Not Lost
Depth to which a ship is immersed in water. The depth varies according to the design of the ship and will be greater or lesser depending not only on the weight of the ship and everything on board, but also on the density of the water in which the ship is lying.
Materials of various types, often timber or matting, placed among the cargo for separation, and hence protection from damage, for ventilation and, in the case of certain cargoes, to provide space in which the tynes of a fork lift truck may be inserted.
Deadweight. Weight of cargo, stores and water, i.e. the difference between lightship and loaded displacement.
A bank of earth or masonry, etc, built to obstruct the flow of water, or to contain it.
dan buoy
An anchored float, ballasted to float upright, carrying a stave through its centre with a flag, a light or other distinguishing mark.
The term is used to imply a danger to surface navigation.
danger angle: horizontal or vertical
The angle subtended at the observer’s eye, by the horizontal distance between two objects or by the height or elevation of an object, which indicates the limit of safe approach to an off-lying danger.
danger line
A dotted line on the chart enclosing, or bordering, an obstruction, wreck, or other danger.
Date Line
The International Date Line, accepted by international usage, is a modification of the 180″ meridian to include islands of any group, etc on the same side of the line. Its position is shown on Chart 5006 — The World — Time Zone Chart and described in the relevant Admiralty List of Radio Signals. cf time zones. When the Date Line is crossed on an E course the date is put back one day, on a W course the date is advanced one day.
See horizontal datum, vertical datum.
A term used in the USA and Canada for a beacon: in the USA it is restricted to unlighted beacons.
Large unlit beacon. Term also used to denote an unlit topmark or other distinguishing mark or shape incorporated into a beacon, light-buoy or buoy.
A relatively small area of greater depth than its surroundings, primarily used for the deeper parts of the great ocean trenches. cf hole.
deep-water route
A route within defined limits which has been accurately surveyed for clearance of sea bottom and submerged obstacles as indicated on the chart. cf recommended track.
A narrow mountain pass or gorge.
degaussing range
An area about 2 cables in extent set aside for measuring ship’s magnetic, fields. Sensing instruments are installed on the seabed in the range with cables leading to a control position ashore. The range is usually marked by buoys.
degenerate amphidrome
A terrestial point on a tidal chart from which co-tidal lines appear to radiate.
A tract of alluvial land, generally trianglular, enclosed and traversed by the diverging mouths of a river.
departure; point of
The last position fixed relative to the land at the beginning of an ocean voyage of passage.
See accretion.
The vertical distance from the sea surface to the seabed, at any state of the tide. Hydrographically, the depth of water below chart datum. cf sounding.
A contrivance for hoisting heavy weights. Usually consisting of a wooden or metal spar with one end raised by a topping lift from a post or mast and the other end pivoted near the base.
Microscopic phytoplankton, especially common in the polar seas; develops delicate cases of silica.
diatom ooze
A siliceous deep-sea ooze formed of the shells of diatoms.
An arrangement of multiple outlets for distributing liquid at the seaward end of a pipeline or outfall.
See dyke.
dilution of precision
A dimensionless number that takes into account the contribution of relative satellite geometry to errors in position determination.
directional radiobeacon
A radiobeacon which transmits two signals in such a way that they are of equal strength on only one bearing.
discoloured water
Colour of the Sea: Variations in colour. The normal colour of the sea in the open ocean in middle and low latitudes is an intense blue or ultramarine. The following modifications in its appearance occur elsewhere:
In all coastal regions and in the open sea in higher latitudes, where the minute floating animal and vegetable life of the sea, called plankton, is in greater abundance, the blue of the sea is modified to shades of bluish-green and green. This results from a soluble yellow pigment, given off by the plant constituents of the plankton. When the plankton is very dense such as when ‘blooms’ occur, the colour of the organisms themselves may discolour the sea, giving it a more or less intense brown or red colour. The Red Sea, Gulf of California, the region of the Peru Current, South African waters and the Malabar coast of India are particularly liable to this, seasonally. The plankton is sometimes killed more or less suddenly, by changes of sea temperature, etc, producing dirty-brown or grey-brown discoloration and ‘stinking water. This occurs on an unusually extensive scale at times off the Peruvian coast.
diurnal inequality
The inequality, either in the heights of successive high waters or in the intervals between successive high or low waters.
diurnal stream
A tidal stream which reverses its direction once during the day.
diurnal tide
A tide which has only one high water and one low water each day; that part of a tide which has one complete oscillation in a day.
The area of water artificially enclosed in which the depth of water can be regulated. Also used loosely to mean a tidal basin (qv).
to dock. To be admitted to a dock.
to dock a ship. To receive a ship into dock, or dry dock.
docks. The area comprising the basins, quays, wharves, etc, and offices of a port; the dock area.
dock sill
The horizontal masonry or timber work at the bottom of the entrance to a dock or lock against which the caisson or gates close. The depth of water controlling the use of the dock is measured at the sill.
That part of a port which contains the facilities for building or repairing ships.
See bollard.
A built-up post, usually of wood, erected on shore or in the water.
berthing dolphins. Dolphins against which a ship may lie. Also known as breasting dolphins.
mooring dolphins. Dolphins which support bollards for a ship’s mooring lines. The ship does not come in contact with them as they are set clear of the berth.
deviation dolphin. Dolphin which a ship may swing around for compass adjustment.
double tide.
A tide which, due to a combination of shallow water effects, contains either two high waters or two low waters in each tidal cycle. At Hook of Holland, this phenomenon occurs with the low waters and is known as the Agger.
In particular, the direction in which the stream is flowing; in general, in rivers and river ports, whether tidal or not, the direction to seaward.
A ship is said to drag (her anchor) if the anchor will not hold her in position. Also commonly used by seamen to describe the retardation of a ship caused by shallow water.
drag sweep
To tow a wire or bar set horizontally beneath the surface of the water to determine the least depth over an obstruction or to ascertain that a required minimum depth exists in a channel. Used as a noun, to denote the apparatus for this.
To deepen or attempt to deepen by removing material from the bottom. Also an apparatus for bringing up bottom samples, gathering deep water organisms, etc.
dredged area. Area where the depths have been increased by the removal of material from the bottom.
dredger or dredge. A special vessel fitted with machinery for dredging, employed in deepening channels, harbours, etc, and removing obstructions to navigation such as shoals and banks. The various types include: Bucket dredgers, Grab dredgers and Suction dredgers.
dredging anchor
A vessel is said to be dredging anchor when moving, under control, with her anchor moving along the seabed.
A feature which is covered and uncovered by the tide is said to dry. The drying height is the height above chart datum, which is indicated on charts by a bar under the figure, or the legend ‘Dries’ which may be abbreviated to ‘Dr’. cf awash.
The distance covered by a vessel in a given time due solely to the movement of current or tidal stream, or both. Also, a detached and floating mass of soil and growth torn from the shore or river bank by floods, often mistaken for a islet. (Common in the East Indies.) (verb) To move by action of the wind and current without control.
drift angle
The angle between the ground track and water track.
drift current
A horizontal movement in the upper layers of the sea, caused by wind. Direct effect of wind. When wind blows over the sea surface, the frictional drag of the wind tends to cause the surface water to move with the wind. As soon as any movement is imparted, the effect of the Earth’s rotation (the Coriolis Force) is to deflect the movement towards the right in the N hemisphere and towards the left in the S hemisphere. Although theory suggests that this effect should produce a surface flow, or ‘wind drift current’ in a direction inclined at 45° to the right or left of the wind direction in the N or S hemisphere, observations show this angle to be less in practice. Various values between 20° and 45° have been reported. An effect of the movement of the surface water layer is to impart a lesser movement to the layer immediately below, in a direction to the right (left in the S hemisphere) of that of the surface layer. Thus, with increasing depth, the speed of the wind-induced current becomes progressively less but the angle between the directions of wind and current progressively increases.
drilling rig
A movable float platform used to examine a possible oil or gasfield.
A ship specially designed for offshore drilling of the seabed.
dry dock
An excavation in the ground, faced with masonry or concrete, into which a ship is admitted for underwater cleaning and repairs. The entrance can be closed by a caisson or gate. The water is pumped out after a vessel has entered, leaving her dry, resting on blocks and generally also supported by shores. Sometimes called a graving dock’. cf floating dock.
dry harbour
A small harbour which dries out, or nearly so, at LW. Vessels using it must be prepared to take the ground on the falling tide.
drying heights
Heights above chart datum of features which are periodically covered and exposed by the rise and fall of the tide, cf awash.
dumb lighter
A lighter incapable of self-propulsion.
dumping ground
An area similar to a spoil ground.
A ridge or hill of dry wind-blown sand which may, or may not, be in a state of migration. Vegetation (frequently planted on purpose) often stabilises previously migrating dunes. Coastal dunes may occur in the vicinity of sandy shores, but cannot survive wave action consequently they are features of the coastland rather than of the foreshore.
(of rise or fall of the tide). The time interval between successive high and low waters.
dyke or dike
A causeway or loose rubble enbankment built in shallow water in a similar way to a training wall, but not necessarily for the same purpose. Sometimes built across shallow banks at the side of an estuary to stabilise the sandbanks by protection against wave action, and to prevent silting in the channel. In the Netherlands: an embankment to prevent flooding and encroachment by the sea. In Orkney and Shetland Islands: a wall. Also used to mean an artificial ditch.

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