Navigation glossary
Common terms and abbreviations used in navigation.
Term |
Meaning |
|---|---|
Active navigation |
Active navigation is the term used when the display is performing navigation to a destination point. The destination point can be a ‘Goto’ (to an onscreen cursor position or a single waypoint), or part of a ‘Follow’ (to a waypoint within a route). |
AIS (Automatic Identification System) |
A tracking system enabling you to receive positional information broadcast by other vessels, and to transmit positional information for your own vessel. AIS is used to identify, locate and track marine vessels in the chart and radar applications. An AIS receiver or transceiver is required to view AIS information. |
Auto range |
A mode that ranges the chart application automatically, to ensure both the vessel and target waypoint are always visible. |
Course Over Ground (COG) |
COG is the actual direction of travel, relative to fixed land. Vessel heading may differ from COG due to the effects of currents, tide and wind. COG is transmitted by GNSS (GPS) receivers. Supported data:
|
Course up (CU / C-up) |
The chart or radar is orientated so as to show your current course directly ahead of your vessel icon. The chart will rotate so that your Course Over Ground (COG) is always upward on the screen. |
Cross Track Error (XTE) |
The amount of deviation from your intended course, expressed as a distance. In the event that you steer off-track, you can create a new course to the target by selecting “Restart XTE” on your pilot controller or multifunction display. |
Direction of Relative Motion (DRM) |
The direction a target is travelling in relation to your own vessel’s direction and speed. |
Follow |
The action whereby the display is placed in active navigation following a route. |
GNSS (Global Navigation Satellite System) |
A constellation of Earth orbiting satellites that can be used to plot latitude, longitude, altitude, Course Over Ground (COG), and Speed Over Ground (SOG). Current available GNSS are:
|
Goto |
The action whereby the display is placed in active navigation travelling to a cursor location or a single waypoint. |
Head up (HU / H-up) |
The chart or radar is orientated so as to show your current heading directly ahead of your vessel icon at all times. As your vessel changes direction, the chart or radar image rotates accordingly to reflect the new bearing. In Head-up, the motion mode is fixed to Relative motion. |
Heading (HDG) |
Compass direction of travel. Heading can be relative to True north or Magnetic north. Heading can be transmitted from a ship’s compass or heading sensor. Supported data:
|
Latitude (Lat) |
A geographic coordinate which indicates the position of a point on the Earth that is either north or south of the equator. When provided as a coordinate, the number of degrees is determined in relation to how far (0° to 90°) north or south the coordinate is from the Earth’s equator — where 90° refers to either the North Pole or South Pole and 0° refers to the equator. One degree of latitude is approximately equivalent to 60 nautical miles. |
Longitude (Lon) |
A geographic coordinate which indicates the position of a point on the Earth that is either east or west of the prime meridian. When provided as a coordinate, the number of degrees is determined in relation to how far (0° to 180°) east or west the coordinate is from the prime meridian. |
North up (NU / N-up) |
The chart or radar image is orientated so that true north is always upward on the screen. As your vessel changes direction, vessel icon (chart) or ship heading line (radar) rotate accordingly to show your relative position to true north. |
Rate of Turn (RoT) |
RoT is the speed at which your vessel turns in a given direction, typically when under autopilot control. |
Relative Motion (RM) |
In the Chart and Radar applications, relative motion mode fixes your vessel’s position and the chart or radar image moves relative to your vessel. In Relative Motion mode you can use the Boat position setting to determine whether the vessel position is fixed in the Center of the chart display or has a Partial offset, or Full offset. Selecting the partial or full offset has the effect of increasing the view ahead. |
Route (RTE) |
A series of waypoints typically used to assist with journey planning and navigation. A route is displayed on screen as a series of waypoints linked by a line. |
Speed of Relative Motion (SRM) |
The velocity of a target relative to your own vessel’s velocity (E.g.: If you are travelling in the same direction as a target, the relative speed will be the difference between your vessel’s speed and the target’s speed. If you are travelling towards / away from each other then relative speed is the combination of both vessel’s speeds). |
Speed Over Ground (SOG) |
The actual speed of travel, relative to fixed land. Vessel speed may differ from STW due to the effects of currents, tide and wind. SOG is transmitted by GNSS (GPS) receivers. Supported data:
|
Speed Through Water (STW) |
The speed of your vessel through the water, also known as boat speed. Due to tide and current this will be different than Speed Over Ground (SOG). STW is measured by a speed transducer. Supported data:
|
Time To Go (TTG) |
The time remaining until you reach the destination point. |
Track |
A visible trail displayed in the Chart app on a multifunction display, showing the passage you have taken. The trail consists of a series of track points which are created automatically. You can save the track to create a permanent record of where you have been. You can also create a new route from a track. |
True Motion (TM) |
True Motion mode fixes the chart position and the vessel icon moves across the screen. As the vessel’s position approaches the edge of the screen, the chart image is automatically redrawn to reveal the area ahead of the vessel. As the vessel’s position approaches the edge of the display, the image is automatically redrawn to reveal the area ahead of the vessel. Note True Motion mode is not available when the orientation is set to “Head-up”. |
Waypoint (WPT) |
A position marked on the screen to indicate a location to navigate to. Waypoint positions are defined by Longitude / Latitude coordinates, and can be saved for future use. As well as acting as position markers, waypoints are also the building blocks used to create routes. Waypoints can be created and displayed in the Chart, Radar, and Fishfinder apps on a multifunction display. |