According to IMO, what should log and speed indicators providing inputs to ARPA equipment be capable of?

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Multiple Choice

According to IMO, what should log and speed indicators providing inputs to ARPA equipment be capable of?

The key idea is that ARPA needs the ship’s motion as it moves through the water, not relative to the ground. The log and speed indicators that feed ARPA must provide the ship’s speed through the water because this value reflects how fast the hull is actually advancing in the water, independent of currents. When ARPA predicts future positions and potential collision threats, it relies on this true through-water speed to project the vessel’s path accurately. If you used speed over ground, currents could make the projection unreliable, since part of the ground speed comes from the water’s movement rather than the ship’s own propulsion. So the correct input is the ship’s speed through the water. Speed over ground, the rate of turn, or maximum speed are not the required inputs for ARPA in this context, as they either include current effects, describe a different parameter, or refer to a limit rather than the actual motion used for plotting and CPA/TCPA calculations.

The key idea is that ARPA needs the ship’s motion as it moves through the water, not relative to the ground. The log and speed indicators that feed ARPA must provide the ship’s speed through the water because this value reflects how fast the hull is actually advancing in the water, independent of currents. When ARPA predicts future positions and potential collision threats, it relies on this true through-water speed to project the vessel’s path accurately. If you used speed over ground, currents could make the projection unreliable, since part of the ground speed comes from the water’s movement rather than the ship’s own propulsion.

So the correct input is the ship’s speed through the water. Speed over ground, the rate of turn, or maximum speed are not the required inputs for ARPA in this context, as they either include current effects, describe a different parameter, or refer to a limit rather than the actual motion used for plotting and CPA/TCPA calculations.

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