Entry & progression
ECDIS is mandatory for this certificate. Not optional, not 'if fitted'. At command level your job is not to operate the ECDIS — it is to set the policy that governs how everyone else operates it, and to know precisely how it lies.
Safety contour and safety depth — get this exactly right
| Setting | What it controls | How it displays |
|---|---|---|
| Safety contour | The boundary between water the system treats as safe and unsafe. Drives the anti-grounding alarms and the look-ahead. | A bold contour line; the shading of the water either side of it changes. |
| Safety depth | The display of spot soundings only. | Soundings shallower than the safety depth are shown in BLACK (bold). Soundings deeper than the safety depth are shown in grey. |
WARNING — Do not invert the sounding rule Under IHO S-52, a spot sounding shallower than your safety depth is BLACK. Deeper soundings go grey and recede. It is the dangerous soundings that are made to stand out. Half the bridge teams afloat have this backwards, and a black sounding they read as 'deep water' is a black sounding they steered over.
Second trap: if the safety contour value you enter does not exist in the loaded ENC, the system uses the next deeper contour available — and it tells you, quietly, in a way that is easy to click past. You asked for 10 m and got 20 m. Everything between is now displayed as safe water. Check what contour the system actually adopted, on every chart, every time.
Setting them, as the master
- Safety depth = draft + squat allowance + your required under-keel clearance. This is the number your soundings are checked against.
- Safety contour = the same figure or greater, chosen from what the ENC actually offers. Never below your safety depth.
- Look-ahead / guard zone set to a distance and width that reflects your speed and turning circle — not the default.
- Run the route check before every departure, and read the output. It is not a formality; it is the machine telling you what your plan crosses.
What ECDIS does not show you
- SCAMIN hides features at small scale. Zoom out and things disappear. They are still there.
- Overscale display: the machine will happily zoom a small-scale ENC to look like a berthing chart. The data does not improve; only the pixels do. Watch for the overscale indicator.
- Standard display is not full display. Objects you might want are hidden until you select 'other' or 'all'. Know what your standing order requires to be visible.
- CATZOC / zone of confidence tells you how much to trust the survey underneath the pretty colours. Much of the world's coastline is charted from leadline surveys older than the vessel.
ECDIS failure
When the ECDIS goes down
- Fix the position by an independent means immediately — radar range and bearing, visual, GNSS on a separate receiver. Do not wait to find out why.
- Reduce speed. Speed is the multiplier on every navigational error you have not yet found.
- Bring up the approved backup arrangement — a second independent type-approved ECDIS, or the paper folio. Know before you sail which yours is, and that it is corrected.
- Revert to manual position fixing at a stated interval and log it.
- Report it. A defective ECDIS is a reportable defect to the company, and potentially to class and port state.
The failure that hurts is not the black screen. It is the ECDIS that keeps running with a bad position input, drawing your ship's outline neatly along a track it is not on.