[CA] [CA11] AIS false positive alarms

[Chuck - Raymarine - Moderator]

Welcome to the Raymarine Forum Steve,

Q1. I believe the reason is the alarm will activate if the traffic CPA is less than a configured range OR the TCPA is less than a configured interval. Do I understand this correctly?
A1. This is indeed correct.

Q2. Is this expected behavior? Is there some other way to prevent these nuisance alarms?
A2. This feature is detailed within Chapter 11.9 Dangerous targets alarm of the LightHouse 3.9 Advanced Operation Instructions. This indeed the expected behavior as the minimum CPA has been violated. The Time to reach safe distance configuration setting is simply configuring how much advance warning the operator may have. Unfortunately, close quarters operation is the nature of the beast many high traffic areas. Should the the AIS Dangerous Targets alarm be left on in such areas, then the results reported may be expected.