Which metric is used by ARPA to assess potential collision with another vessel?

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Multiple Choice

Which metric is used by ARPA to assess potential collision with another vessel?

ARPA evaluates collision risk by predicting how two vessels will move relative to each other, using the predicted minimum separation and when it would occur. The essential metrics are the Closest Point of Approach and the Time to Closest Point of Approach. CPA is the smallest predicted distance between your vessel and the other vessel if both maintain their present speeds and courses. TCPA is the time at which that closest approach would happen. Together, these tell you whether an encounter is likely to be safe or requires action, and they are calculated directly from the vessels’ speeds, courses, and positions as shown by the radar/ARPA. Wind speed, depth soundings, and engine RPM don’t measure how two ships will approach each other on the radar. Wind speed is environmental data, depth soundings relate to water depth, and engine RPM is about propulsion, not the predicted relative motion used to assess collision risk.

ARPA evaluates collision risk by predicting how two vessels will move relative to each other, using the predicted minimum separation and when it would occur. The essential metrics are the Closest Point of Approach and the Time to Closest Point of Approach. CPA is the smallest predicted distance between your vessel and the other vessel if both maintain their present speeds and courses. TCPA is the time at which that closest approach would happen. Together, these tell you whether an encounter is likely to be safe or requires action, and they are calculated directly from the vessels’ speeds, courses, and positions as shown by the radar/ARPA.

Wind speed, depth soundings, and engine RPM don’t measure how two ships will approach each other on the radar. Wind speed is environmental data, depth soundings relate to water depth, and engine RPM is about propulsion, not the predicted relative motion used to assess collision risk.

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