- 12 hour time
- 12 hour time breaks a day up into two 12 hour parts. Am is the morning from midnight to midday and pm is the afternoon from midday to midnight.
- 24 hour time
- 24 hour time tells the time over 24 hours in a day from 0000 to 2359. The first two digits are the hours and the second two digits are the minutes.
- alternating light
- An alternating light changes from one colour to another.
- Australian Hydrographic Service
- The Australian Hydrographic Service make marine charts in Australia.
- bearing
- Bearing is the direction of a landmark from a boat.
- Beaufort scale
- A scale to describe the speed and effects of wind.
- cardinal mark
- Cardinal marks show the direction of safe water.
- cardinal points
- The cardinal Points North East South West are used to give directions.
- chart datum
- The lowest possible tide for an area. Depths on a chart are measured from chart datum.
- chart scale
- Chart scale is on the sides of a marine chart. Chart scale is used to find coordinates, plot position and measure distance.
- charted depth
- Depth of the water written on a marine chart. This is the depth on the lowest astronomical tide for that area.
- cold front
- The leading edge of cool air pushing under warm air creating storms, wind and rain.
- compass error
- Compass error is change to a compass reading caused by the earths magnetic field (variation) or magnetic objects near a compass (deviation).
- compass rose
- A circle used to show direction with degrees or cardinal points.
- contour lines
- Contour lines are lines of the same water depth shown on a marine chart. On land, contour lines show the same elevation.
- coordinate
- A coordinate locates a position on a grid.
- course
- A course is a direction or path that you want a boat to travel.
- course over ground
- Course over ground is the course in degrees over the ocean floor that you want you boat to travel.
- course to steer
- The course to steer is a true course from a chart adjusted for compass error. It is the course in degrees to steer on your compass.
- decimal
- A decimal number is broken into tenths, hundredths, thousandths etc.
- degree
- Degrees are used to measure angles, give direction and plot coordinates on a chart.
- degrees
- Degrees are used to give direction, there are 360 degrees in a circle.
- diurnal tide
- A diurnal tide has one high and one low tide in a day.
- draft
- Draft is the depth of the hull in the water.
- drying area
- An area that covers and uncovers with the tide.
- drying height
- Drying height is the height above the lowest tide when a rock sandbar or mudflat dries. Shown on a marine chart with an underlined number.
- elevation
- Elevation is the height of a landmark above high tide.
- equator
- The Equator is the line of latitude at 0°. Latitude is measured North or South of the Equator.
- fetch
- Fetch is the distance the wind has blown over water. Longer fetch makes bigger waves.
- fix
- A fix uses compass bearings to plot your position on a chart.
- fixed light
- A fixed light is always on.
- flashing light
- A flashing light has dark longer than light.
- fraction
- A fraction is part of a whole e.g. half.
- fuel consumption
- Marine fuel consumption is measured in litres per hour.
- gauge
- A gauge is an instrument that measures and gives a display of the amount, level, or contents of something. E.g. a fuel gauge.
- gravity
- Gravity is the force that pulls toward the centre of the earth or moon.
- ground track
- The ground track is path over the ocean floor that your boat travels.
- Heading
- Heading is direction the boat is pointing.
- hectopascals
- A hectopascal is a unit of measurement for air pressure.
- high pressure system
- A high pressure system is an area of high pressure that rotates anti-clockwise in the southern hemisphere.
- horizontal
- Horizontal means flat or across.
- isobar
- An isobar is a line of equal pressure draw on a synoptic chart.
- isolated danger mark
- A red and black marker used to show a danger on its own.
- isophase light
- An isophase light has light and dark the same length of time.
- knots
- Knots are the marine measurement of speed. One knot is one nautical mile per hour.
- lateral marks
- Lateral marks are green or red markers that show channels of deeper water.
- latitude
- Latitude and longitude make an imaginary grid over the earth. Lines of latitude run horizontally. Lat is flat.
- leg
- A leg is a path between two waypoints.
- longitude
- Latitude and longitude make an imaginary grid over the earth. Lines of longitude run up and down from pole to pole.
- low pressure system
- A low pressure system is an area of low pressure that rotates clockwise in the southern hemisphere.
- lowest astronomical tide
- The lowest possible tide for an area.
- magnetic deviation
- Magnetic Deviation is compass error caused by metal, magnets or objects near a compass.
- magnetic north
- Magnetic north is made by the earths magnetic field. It is different to true north.
- magnetic variation
- Magnetic variation is compass error caused by the earths magnetic field.
- marine chart
- A marine chart is a map used to navigate on the ocean.
- minute
- A minute is 1/60th of a degree. A minute can also mean 1/60th of an Hour.
- mixed tide
- A mixed tide is in between a diurnal and semidiurnal tide.
- monsoon trough
- The monsoon trough is a seasonal trough that forms over northern Australia in the wet season creating heavy rain, storms and sometimes cyclones.
- nautical mile
- Nautical miles are used to measure distance on the ocean. A nautical mile is one minute of latitude or 1.85 km.
- neap tide
- A neap tide is a tide just after the first or third quarters of the moon when there is least difference between high and low water.
- notices to mariners
- Notices to Mariners show changes to a marine chart.
- occulting light
- An occulting light has light longer than the dark.
- percent
- Percent is a fraction out of 100.
- port
- Port is the left side of the boat when facing forward.
- port hand mark
- A port hand mark is a red lateral mark kept to port when travelling upstream.
- position
- Position is the location of a boat given as a coordinate or distance and direction from a landmark.
- prime meridian
- Line of longitude at 0° at Greenwich, England. Longitude is measured east or west of the Prime Meridian.
- range (light)
- The range is the distance when a light can be seen in clear visibility.
- safe water mark
- A red and white marker showing safe water or the entrance to a marked channel.
- seas
- Seas are waves caused by local winds.
- semi-diurnal tide
- A semidiurnal tide has two high and two low tides in a day.
- special mark
- A special mark is a marker for different reasons such as a pearling lease, aquaculture, yacht racing area and so on.
- spring tide
- A spring tide is a tide just after a new or full moon, when there is the greatest difference between high and low water.
- starboard
- Starboard is the right side of the boat when facing forward.
- starboard hand mark
- A starboard hand mark is a green lateral mark kept to starboard when travelling upstream.
- swell
- Swell is waves made by distant storms that travel from a long distance away.
- synoptic chart
- A synoptic chart is a map of pressure difference and weather systems at sea level.
- title block
- The title block shows the name and location of the chart.
- trough
- A trough is a line of low pressure creating winds and unsettled stormy weather. A trough can also mean the low point between two waves.
- true north
- True north is at the North Pole. True north is up on a marine chart.
- under keel clearance
- Under keel clearance is the distance between the hull of a boat and the ocean floor.
- volume
- Volume is the amount of something that a container can hold e.g. the fuel tanks has a volume of 25 litres.
- warm front
- The leading edge of warm air pushing over cool air creating rain and wind.
- waypoint
- A waypoint is a point on a course.
- whole number
- A number without a decimal point.