CPA (Closest Point of Approach)
Abbreviation: CPA
The minimum distance between own ship + a target — a primary radar/ARPA collision-risk indicator.
Regulatory detail & full definition
Closest Point of Approach is the minimum predicted distance between own ship + a target vessel if both maintain course + speed. CPA is displayed by ARPA + ECDIS + AIS-integrated systems. Standard OOW practice sets CPA alarms at 1-2 NM in open water, tighter in coastal + confined water. See /glossary/tcpa for the time-to-CPA.
Authoritative source: IMO — Radar + ARPA ↗
Related
Source: IMO ARPA performance standard
High confidence
Editorial confidence: how we grade.