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abaft

in a direction toward the stern

abeam

on the beam; a direction at right angles to the keel.

aboard

in or on board a vessel

abreast

side by side

afloat

a vessel wholly supported by water and off the bottom

aft

at or towards the stern

ahead

in the direction of the vessel's head or bow

aid to navigation

a device or object, external to the vessel, located to assist safe navigation. It may be man-made or natural

amidships

in the middle of the ship, whether longitudinally or laterally.

anchor

a device designed to hold a ship in any desired location by temporarily attaching it to the seabed by means of a rode

angle of cut

the angle at which two lines of position on a chart intersect

angular distance

the size of an angle, measured in degrees and fractions of a degree

apparent wind

the direction of the wind as it appears on board. It differs from the true wind direction due to the vessel's motion

astern

(1) in back of, or behind the boat; (2) the movement of a ship going backwards

ballast

added weight in a ship's bottom to provide stability and trim

beacon

a distinctive artificial structure erected as an aid to navigation

beam

the maximum width of a vessel

bearing

the direction in which an object lies with respect to a reference direction

belay

to make fast a line without knots by taking turns round a cleat or belaying pin

bifurcation buoy

a buoy marking where a channel divides

buoy

a floating mark anchored to the bottom, used as an aid to navigation

cardinal buoy

an aid to navigation that indicates the cardinal direction of safe water

chart

a "map" of a sea area showing any coastal lines and used specifically for nautical navigation

chock

(1) a deck fitting used to change the direction of tension of an anchor rode or mooring line; (2) a fitting designed to receive an object and hold it securely

cleat

a fitting with two arms or horns to which lines are made fast

close aboard

beside, close to, alongside

close-hauled

sailing as close as possible to the direction of the wind

con

to steer the boat by direct observation of landmarks

correcting

the conversion of courses or bearings from compass to magnetic to true

current

the horizontal movement of the water

danger zone

the sector extending from dead ahead to 22.5 degrees abaft the starboard beam, an arc of 112.5 degrees in all

dead reckoning

the process of determining a vessel's position, using only knowledge of speed, elapsed time, course steered, and a point of departure

deviation

the angular difference between magnetic north and compass north

discharge current

the water expelled by the propeller

displacement

the weight of the volume of water displaced by a floating vessel

downwind

to leeward. The direction in which the wind is blowing

ebb

a current generally from the land towards the open ocean, associated with a falling tide

fairway buoy

a buoy that marks a landfall, the entrance to a channel, or the centre of a channel

fender

a device hung over the side of a vessel to protect the hull from other objects

fix

an accurately known position found by taking new observations

flood

a current generally from the open ocean towards the land, associated with a rising tide

freeboard

the minimum vertical distance between the gunwale and the waterline

give way

to keep out of the way of another vessel

knot

(1) a unit of speed equal to one nautical mile per hour; (2) the tucks and loops in a line used to fasten it to an object or to itself

lateral buoyage system

a buoyage system in which different coloured buoys are used to mark the sides of a channel

latitude

the angular distance of any point on the earth's surface north or south of the equator, as measured at the earth's centre

lee side

the side opposite to the direction from which the wind blows

leeward

away from the wind

line of position

a line on which the vessel is known to be

longitude

the angular distance of any point on the earth's surface east or west of the prime meridian, as measured at the polar axis

magnetic north

the north direction indicated by an isolated magnetic compass for which the deviation is nil

magnetic pole

one of the two geographical areas, north and south, where the earth's magnetic field enters or leaves the earth

meridian

an imaginary line on the surface of the earth joining the north and south geographic poles

nautical mile

a unit of distance defined as 1852 metres, equivalent to the length of one minute of latitude

navigational aid

an apparatus on board a boat that will assist in navigating

pillar buoy

a very large structural buoy that may have a light, bell or whistle.

plot

to draw lines on a chart, indicating bearings, courses and positions.

port

a vessel's left side when facing forward

prime meridian

the meridian of longitude that passes through Greenwich, England

range

(1) two aids to navigation which, when seen to be in line establish a line of position; (2) the difference in height between high and low tides

reaching

sailing with the wind approximately on the beam

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