Radar Observer and ARPA: An Overview for Deck Officers
Radar Observer and ARPA endorsements are required for most deck officer licenses. This overview explains what each covers, how they differ, and how mariners keep them current.
Why Radar Endorsements Matter
Radar is a core collision-avoidance and navigation tool, and the USCG requires deck officers standing navigational watches on radar-equipped vessels to hold a Radar Observer endorsement. It certifies that you can interpret a radar display, plot targets, and use radar to navigate safely and avoid collisions in reduced visibility.
Radar Observer Course Types
Radar Observer endorsements come in route-specific flavors — commonly Unlimited (oceans/near-coastal), Inland, and Rivers — matched to where you sail. The training combines radar theory, manual plotting, and target-motion analysis. Which endorsement you need depends on the routes your license authorizes.
What ARPA Adds
ARPA — Automatic Radar Plotting Aid — is a system that automatically tracks targets and computes their course, speed, closest point of approach, and time to closest approach. The ARPA endorsement, an STCW competency, certifies you can operate and interpret ARPA correctly, understand its limitations, and not over-rely on automation. It's required for officers on ARPA-equipped internationally trading vessels.
How They Fit Your License
Radar Observer is typically required to earn and exercise most deck officer licenses, and ARPA is added for STCW-governed roles on equipped vessels. Newer navigation competencies like ECDIS often accompany these as officers move up in tonnage and onto ocean routes. Together they form the electronic-navigation backbone of an officer's qualifications.
Keeping Them Current
The Radar Observer endorsement has a defined validity period and must be renewed through a refresher course or, in some cases, documented recent radar service before it expires. Letting it lapse can prevent you from standing watch, so track its date alongside your STCW and medical renewals.
A note on requirements
Credentialing rules change and often depend on your specific vessel, route, tonnage, and history. Nothing here is legal advice. Always confirm the current requirements with the USCG National Maritime Center (NMC) and with your employer or vessel operator before making career or hiring decisions. When a rule seems to conflict with your situation, an NMC deficiency letter or a call to the NMC Customer Service Center is the fastest way to get an authoritative answer.