Question 1

IMO's S-100 is best described as what, relative to the existing S-57 ENC standard?

Accepted Answer

A successor framework — a family of data product specifications (of which an updated electronic chart standard, S-101, is one) designed to support richer, more flexible digital navigational and marine data products than the older single-purpose S-57 ENC format S-100 is a broader, more flexible universal hydrographic data framework than S-57 — it supports multiple linked data product specifications (S-101 for the next-generation ENC, plus others for tides, currents, bathymetric surface data, etc.) rather than S-57's single rigid chart-only format. Navigators should expect ECDIS systems to transition toward S-100-based products over the coming years, requiring updated software/hardware capability.

Question 2

You're preparing a passage plan for a coastal leg in a yacht drawing 3.2m. At one point the chart shows a least depth of 3.8m at chart datum. What MUST you check before finalising this leg?

Accepted Answer

The tidal height at the time of transit to confirm sufficient under-keel clearance Charted depths are referenced to chart datum (often LAT), so you must add the predicted tidal height for your transit time to get the actual depth, then compare to your draft plus a safety margin to confirm UKC.

Question 3

During your watch the ECDIS gives a "safety contour crossing" alarm. What is the correct response?

Accepted Answer

Assess the situation against the planned route and charted depths, take action to maintain safe water, and inform the Master if there is any doubt A safety contour alarm indicates the vessel may be approaching water shallower than the set safety contour. It must be investigated against the route and charted information, with avoiding action taken and the Master informed as appropriate — never simply silenced.