Glossary

 

From ‘absolute bearing’ to ‘yaw’. If you are coming across marine terminology for the first time, our SIMRAD A-Z of online terms explains what they mean.

A-B

Absolute Bearing

Absolute bearing refers to the angle between the magnetic north (magnetic bearing) or true north (true bearing) and an object.

AIS

See Automatic Identification System

 

Anenometer

An instrument used for measuring wind speed and direction. A fixed anenometer is often also called a Wind Sensor – data from this instrument can be displayed widely across the Simrad range.

Apparent Wind

The aggregate term describing Apparent Wind Angle and Apparent Wind Speed.

Apparent Wind Angle

The wind direction as it is detected on a moving platform like a boat. It is the vector that results from the combination of weather generated wind (True Wind) and the direction and speed of the boat through the air. Abbreviated AWA.

Apparent Wind Speed / AWS

The wind speed as it is detected on a moving platform like a boat. It is the aggregate wind velocity that results from the combination of weather generated wind (True Wind) and the direction and speed of the boat through the air. Abbreviated AWS.

AWA

See Apparent Wind Angle.

Automatic Identification System

An automated tracking system that broadcasts vessel identification, position, speed and course data to assist marine traffic management and search and rescue among other purposes. Abbreviated AIS.

Azimuth

An angular measurement between a celestial body like a star or satellite and the North, measured clockwise around the observer's horizon.

Bathymetric Chart

A visual representation of the underwater terrain that uses Depth Contours and (typically) different shades of colour to indicate the shape of the water bed, such as you will find on the water areas of a maritime chart. 3D Bathymetric Charts visualise the same data in a three-dimensional representation to enhance understanding of the bottom shape.

Beam Sea

A sea condition with waves at approximate right angles to the boat's heading.

Bear Away

Turn a vessel away from the wind. Also known as Bear Down. 

Bear Up

Turn a vessel away from the wind. Also known as Bear Down. 

Bearing

The direction in degrees on a True North or Magnetic North compass rose between an object like a boat or observer, to another point see Relative Bearing) or to magnetic or true north (see Absolute Bearing). Abbreviated as BRG on marine electronics – but note this commonly refers to a Relative Bearing between the boat and a point such as a waypoint.

Bearing to Mark

The Relative Bearing between a boat's current position and the chosen Mark. Abbreviated BTM.

Bearing to Waypoint

The Relative Bearing between a boat's current position and the chosen Waypoint. Abbreviated BTW.

BRG

See Relative Bearing.

BTM

See Bearing to Mark.

BTW

See Bearing to Waypoint

 

C-D

Cardinal Marks

The four points of the compass – North, South, East and West

Celestial navigation

Navigation by the position of the stars, sun and moon

Chartsum

Calculation undertaken to ensure data is accurate

COG

See Course Over Ground

Course

Planned route to a destination, Waypoint or Mark

Course Bearing

The Course Bearing is the bearing to remain on a leg of a course

Course Over Ground

The direction of progress of a vessel, with respect to the Earth's surface. 

Cross Track Distance

Defined as the closest distance from the proximity station, to the planned navigation route

Cross Track Error

The distance the vessel is to one side or the other of the course between two waypoints

CTS

See Course to Steer

Dead Reckoning

A method of navigation estimating a vessel's position from the distance run measured by the log and course steered

Depth Contour

A line that joins points of identical depth

DR

See Dead Reckoning

DTG

Distance to Go - When navigating to a Waypoint, DTG indicates the remaining distance from your present position to the next Waypoint

DTM

Distance to Mark

DTW

Distance to Waypoint

E-F

ECDIS

Electronic Chart Display and Information Systems – a standard set by the IMO to govern electronic navigation equipment as an alternative to paper charts. Typically applicable for commercial vessels.

EPIRB

Emergency Position Indicator Radio Beacon

ETW

Estimated time to Waypoint

Fathom

A measurement of 6 feet or 1.8 metres

G-H

GLONASS

GLONASS is a Russian space-based satellite navigation system operating as part of a radionavigation-satellite service. It provides an alternative to GPS and is the second navigational system in operation with global coverage and of comparable precision

GNSS

Global Navigation Satellite System

GPS

 

Green to Green

Vessels moving in the opposite direction on their starboard sides

Hard

Section of shoreline suitable for mooring or hauling out

Heading (HDG)

The direction in which the nose of the vessel is heading - not necessarily the same as the direction the vessel is actually moving

Head Sea

A sea in which the waves are directly opposing the motion of the vessel

Heavy Weather

Combination of high seas and rough winds making for dangerous passage

I-J

IMO

International Maritime Organization, the body based in London that sets internationally adopted maritime standards and laws like the ColRegs

Inshore

Water that is typically close to or within sight of the shore

K-L

Knot

Unit of speed equivalent to 1 nautical mile - 1.8520km or 1.1508 mi per hour

Lateral system

A system of aids to navigation whereby characterisitcs of buoys and beacons indicate the sides of a channel or route

Latitude

The angular distance of a place north or south of the earth's equator, or of the equator of a celestial object.  Expressed in degrees and minutes

 

Laylines

A straight line, or bearing, extending from a mark or waypoint to indicate the course the vessel should take to pass to the windward side of the mark

Lay to

To bring a vessel into the wind and hold her stationary

League

A measurement of three nautical miles

Leg

A segment of a route between two waypoints

Longitude

The angular distance of a place east or west of the Greenwich meridian.  Expressed in degrees and minutes

 

M-N

Magnetic bearing

An absolute bearing using magnetic north

Magnetic North

The direction towards the North Magnetic Pole

Magnetic variation

The angle between magnetic north as shown by a compass and True North

See Simrad HS60 GPS compass / Compass products

Mark

Typically, a featured point on a chart that hasn't been set by a user. Common examples include navigation, danger or sailing buoys.

MFD

Mutlifunction Display

MOB

Man Overboard, an emergency situation requiring assistance

Nautical mile

A unit of length approximating to one minute of arc of latitude andloong any meridian arc

NFU

Non Follow Up

See NF80 Non follow up remote

ND

NoDrift instruction on autopilot

O-P

Onshore

A wind that is blowing from the sea towards the land.

Point

A unit of bearing equal to 1/32 of a circle - or 11.23 degrees

Polar %

Boat speed predictions across a variety of wind speeds

Q-R

Quartering Sea

Seas approaching a vessel from between 105˚ and 165˚ to port or starboard

Radar

Abbreviation of RAdio Detection And Ranging

See Simrad Radars

Relative Bearing

The horizontal direction in degrees (True North or Magnetic North) from an object like a boat or observer, to another point see Relative Bearing) or to magnetic or true north (see Absolute Bearing). Abbreviated as BRG on marine electronics – but note this commonly refers to a Relative Bearing between the boat and a point such as a waypoint.

RNC

Raster Navigation Charts - a scan of a paper chart

See C-MAP charts

Reaching

Driving the vessel across the wind

S-T

Set

The direction toward which the current flows

Set HDG

Set Heading instruction on autopilot

Sextant

A navigational instrument used to measure a ship's latitude

Shift tides

Sighting the position of the sun abd moon using a sextant, referencing a nautical almanac to determine the location and phase of the moon and calculating the relative effect of the tides on the navigation of the vessel

Shoal

Shallow water presenting a hazard to navigation

Shoal draught

An especially shallow draught of a vessel - capable of negotiating unusually shallow water

Slack tide

The period between rising tie or falling tide - or falling tide and rising tide

Slip

A place for a vessel to launch or moor

SOG

Abbreviation od Speed Over Ground, the speed of the vessel relative to the earth

Sounding

Measuring the depth of the warer

 

Springs

Big tides caused by the alignment of the moon and the sun

STW

Abbreviation of Speed Through Water

Track (TRK)

The path of the vessel

Trim

The relationship of a ship's hull to the waterline

See our Instruments page

True Bearing

An absolute bearing using true north

True North

The direction of the geographical North Pole

TW

True Wind

TWA

True Wind Angle

TWD

True Wind Direction

TWS

True Wind Speed

U-V

Upbound

A vessel travelling upstream

UTC

Coordinated Universal Time

Vector Charts

Charts displayed by the plotter from stored data points

See C-MAP Reveal

W-X

Waft

Signal flag on a vessel

Wake

Turbulence behind a vessel.

Waypoint

Location defined by navigational coordinates, part of a planned route. Waypoints can be actual things but also virtual spots in the middle of the ocean.

Learn more about waypoints on these videos: 

Create and manage Waypoints

How to plot a course, make a route, set waypoints

NSS Waypoint management

Create a Waypoint from a sonar or radar screen

Weather side

The side of the vessel exposed to the wind

Weigh Anchor

To heave up or lift the anchor preparatory to sailing

Wheelhouse

Location on a vessel where the sheel or controls are situated, also called the pilothouse or bridge

Wind Sensor

See Anenometer

Wind-over-tide

Sea conditions with a tidal current and a wind in oppositite directions resulting in short heavy seas

Windage

Wind resistance of the boat

Windward

In the direction the wind is coming from

XTE

See Cross Track Error

Y-Z

Yaw

A vessel's rotational motion around a vertical axis