Page 100 - Electronic Navigation Cyber Book

IMO standards require that certain alarms be available on the ECDIS.
Among these are:
1. Deviating from a planned route.
2. Chart on a different geodetic datum from the positioning
system.
3. Approach to waypoints and other critical points.
4. Exceeding cross-track limits.
5. Chart data displayed overscale (larger scale than
originally digitized).
6. Larger scale chart available.
7. Failure of the positioning system.
8. Vessel crossing safety contour.
9. System malfunction or failure.
Alarms consist of audible and visible warnings. The navigator
may determine some setpoints. For example, he may designate a safety
depth contour or set a maximum allowed cross-track error. Operational
details vary from one system to another, but all ECDIS will have the basic
alarm capabilities noted. The navigator is responsible for becoming
familiar with the system aboard his own ship and using it effectively.

ECDIS Units
The following units of measure will appear on the ECDIS
chart display:

• Position: Latitude and Longitude will be shown in degrees, minutes,
and decimal minutes, normally based on WGS-84 datum.
• Depth: Depth will be indicated in meters and decimeters.
Fathoms and feet may be used as an interim measure only:
• when existing chart data is held in those units only,
• when there is an urgent need for an ENC of the applicable area, and
• time does not allow for an immediate conversion of
the English units to their metric equivalents.
• Height: Meters (preferred) or feet.
• Distance: Nautical miles and decimal miles, or
meters.
• Speed: Knots and decimal knots.

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