Your ARPA has automatic speed inputs from...

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Question 1 of 2066636ee928f7522a1c519198

Your ARPA has automatic speed inputs from the log. Due to currents, the log is indicating a faster speed than the speed over the ground. What should you expect under these circumstances?

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Question 1 of 20

66636ee928f7522a1c519198

Your ARPA has automatic speed inputs from the log. Due to currents, the log is indicating a faster speed than the speed over the ground. What should you expect under these circumstances?

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🔍 Key Concepts

• ARPA (Automatic Radar Plotting Aid) inputs: difference between log speed (through the water) and speed over ground (SOG) in current • How CPA (Closest Point of Approach) and TCPA (Time to CPA) are calculated from relative motion • Effect of an incorrect own-ship speed input on true vectors vs relative vectors

💭 Think About

• Think about whether ARPA uses your ship’s speed through the water or speed over the ground when it computes true motion and CPA/TCPA. • If your ARPA thinks you are going faster than you really are, will it predict that you and the target will meet earlier or later than in reality? • Consider which is more sensitive to an error in own-ship speed input: the target’s displayed true course vector, the time estimate to CPA, the distance at CPA, or the detection/acquisition range.

✅ Before You Answer

• Verify how CPA is defined: is it a distance or a time? Don’t confuse it with TCPA. • Check which ARPA output directly depends on an accurate own-ship speed and course to compute true vectors. • Confirm whether the radar detection/acquisition range is affected by your own-ship speed input, or by other factors like power, height of eye, and target size.

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Question 1 of 2066636ee928f7522a1c519198

Your ARPA has automatic speed inputs from the log. Due to currents, the log is indicating a faster speed than the speed over the ground. What should you expect under these circumstances?

Back

Question 1 of 20

66636ee928f7522a1c519198

Your ARPA has automatic speed inputs from the log. Due to currents, the log is indicating a faster speed than the speed over the ground. What should you expect under these circumstances?

No comments yet

Be the first to share your thoughts!

If the question has a related picture, it will appear here.

🔍 Key Concepts

💭 Think About

✅ Before You Answer

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