Radar OSA Practice Test

ARPA is the term used for ships' navigation interfaces because it denotes the radar-based plotting system that directly interacts with the navigator. Automatic Radar Plotting Aid automatically plots other vessels on the radar display, calculates relative motion, and shows predicted tracks, CPA (closest point of approach), and TCPA (time to CPA). This gives the navigator a concrete interface to assess collision risk and plan maneuvering, making it the standard navigation interface on many ships.

The other terms don’t describe a navigation interface: Dynamic is associated with movement control systems like Dynamic Positioning, not an interface for charting or tracking targets; Voyage refers to a voyage or route, not an on-screen interface; Safety is a broad goal rather than a specific navigation interface.