Presumably, route planning takes place before the voyage begins, except in situations where major changes in the route are called for while the ship is underway. In either case, both ECDIS and ECS will allow the display of the smallest scale charts of the operating area and the selection of waypoints from those charts. ECDIS requires a warning that a chosen route crosses a safety contour or prohibited area; ECS will not necessarily do so. If the data is raster, this function is not possible. Once the waypoints are chosen, they can be saved as a route in a separate file for later reference and output to the autopilot.

It is a good idea to zoom in on each waypoint if the chart scale from which it is selected is very small, so that the navigational picture in the area can be seen at a reasonable scale. Also, if a great circle route is involved, the software may be able to enter the waypoints directly from the great circle route file. If not, they will have to be entered by hand.

During route monitoring, ECDIS must show own ship's position whenever the display covers that area. Although the navigator may chose to "look-ahead" while in route monitoring, it must be possible to return to own ship's position with a single operator action. Key information provided during route monitoring includes a continuous indication of vessel position, course, and speed. Additional information that ECDIS or ECS can provide includes distance right/left of intended track, time-to-turn, distance-toturn, position and time of "wheel-over", and past track history.

As specified in Appendix 5 of the IMO Performance Standard, ECDIS must provide an indication of the condition of the system and its components. An alarm must be provided if there is a condition that requires immediate attention. An indication can be visual, while an alarm must either be audible, or both audible and visual.

The operator can control certain settings and functions, some of the most important of which are the parameters for certain alarms and indications, including:

• Cross-track error: Set the distance to either side of the track the vessel can stray before an alarmsounds. This will depend on the phase of navigation, weather, and traffic.
• Safety contour: Set the depth contour line which will alert the navigator that the vessel is approaching shallow water.
• Course deviation: Set the number of degrees off course the vessel's heading should be allowed to stray before an alarm sounds.
• Critical point approach: Set the distance before approaching each waypoint or other critical point that an alarm will sound.
• Datum: Set the datum of the positioning system to the datum of the chart, if different.

• What is the Automatic Identification System (AIS)? - 2010-01-08 - 06:30:48
• Aids to Radar Navigation - 2009-04-22 - 03:18:46
• Radar Navigation - Recognition of Unwanted Echoes - 2009-04-22 - 02:44:30
• Factors Affecting Radar Interpretation - 2009-04-22 - 02:13:00
• Radio Wave Spectra - 2009-04-22 - 01:33:00
• Using Electronic Chart - Training and Simulation - 2009-04-17 - 11:23:17
• Using Electronic Chart - Waypoints and Routes - 2009-04-17 - 01:07:15
• Warship ECDIS - 2009-04-17 - 01:00:18
• The Importance of Electronic Charts - 2009-04-17 - 12:55:31

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