What determines when to trust the ARPA-provided CPA/TCPA values?

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CPA and TCPA come from the ARPA track of the target, so how much you can trust those values depends on how solid that track is. Track quality reflects how reliable the radar measurements are for that target—clear, consistent range and bearing updates with a stable return and little clutter or misidentification. Confidence is about how well the tracker believes its motion model fits the target’s actual movement and how secure the track is over time (for example, whether the target remains tracked through several sweeps or shows maneuvering that the model hasn’t yet captured). When both track quality and confidence are high, the calculated CPA and TCPA are trustworthy for collision avoidance decisions. If the track is poor—occasional detections, rapid changes, clutter, or loss of lock—the CPA/TCPA can be misleading, and you should not rely on them alone until the track improves or you corroborate with other information like AIS or another sensor. Vessel color or time of day and AIS age don’t affect the trust in ARPA-derived values.