Question 1

On a synoptic chart, isobars are drawn much closer together in one area than another. What does this tell you about wind conditions in the tightly-packed area?

Accepted Answer

Wind will be stronger there — closely-spaced isobars indicate a steeper pressure gradient, which drives stronger wind The pressure gradient — how quickly pressure changes with distance — is what drives wind. Closely-spaced isobars mean pressure is changing rapidly over a short distance (a steep gradient), which produces stronger winds; widely-spaced isobars mean a gentle gradient and lighter winds. This is a basic but frequently-tested chart-reading skill at every level from Yachtmaster upward.

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.