If your speed input is incorrect, what effect would it have on your ARPA data?

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Multiple Choice

If your speed input is incorrect, what effect would it have on your ARPA data?

The main idea is that ARPA converts the radar’s relative motion into true motion by using your own ship’s speed and course. If the speed you input is wrong, that conversion is done with the wrong reference motion, so the computed true vectors for each target—its true course over ground and true speed over ground—become biased. The radar will still report range and bearing, and it may show relative motion, but any values that depend on transforming to earth-centered vectors will be incorrect. ARPA doesn’t automatically fix this just from the radar data; the error persists until the speed input is corrected. The incorrectness of the true vectors is the key impact, rather than the raw range measurement itself.

The main idea is that ARPA converts the radar’s relative motion into true motion by using your own ship’s speed and course. If the speed you input is wrong, that conversion is done with the wrong reference motion, so the computed true vectors for each target—its true course over ground and true speed over ground—become biased. The radar will still report range and bearing, and it may show relative motion, but any values that depend on transforming to earth-centered vectors will be incorrect. ARPA doesn’t automatically fix this just from the radar data; the error persists until the speed input is corrected. The incorrectness of the true vectors is the key impact, rather than the raw range measurement itself.

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