What is the fundamental difference between an ENC (Electronic Navigational Chart) and an RNC (Raster Navigational Chart), and why does it matter for ECDIS route planning?

A. There is no meaningful difference; both behave identically in ECDIS

B. An ENC is a vector chart built from structured, queryable data (allowing features like safety contour selection, automated route checking against depths/hazards, and layered display), while an RNC is essentially a scanned image of a paper chart with no underlying queryable data — an ECDIS operating on RNC data alone cannot perform automated route-checking/safety-contour functions in the way it can with genuine ENC coverage

C. RNC charts are always more accurate than ENC charts

D. ENC data is only used for planning, never for real-time monitoring

A. The tidal height at the time of transit to confirm sufficient under-keel clearance

B. The yacht's fuel consumption for that leg

C. The colour of the seabed shown on the chart

D. Only the distance to the next waypoint

A. Switch the ECDIS to standby mode and navigate by GPS position alone

B. Ignore it — ECDIS alarms are frequently false and can be left running

C. 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

D. Acknowledge and silence the alarm immediately so it does not distract the helmsman