Why does Gard treat AIS and radar plotting as genuinely different, complementary methods rather than two ways of getting the same answer?

A. Radar is simply an older, less accurate version of AIS and is kept only as a legacy backup

B. AIS calculates collision risk from dynamic data broadcast by both vessels (course, speed, position from each vessel's own sensors); radar plotting independently evaluates how a target is actually moving relative to your own ship — a different method that can catch what AIS sensor errors would hide

C. AIS and radar plotting use identical underlying data, so cross-checking one against the other has no real value

D. Radar plotting is only relevant in restricted visibility and has no role when AIS is available

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