Automatic Radar Plotting Aid – Officer of the Deck Phase (ARPA - OOD) Phase 1 Practice Test

ARPA must be operable on two range scales, one for close-in navigation and one for distant monitoring. This ensures you can track targets as they come in for immediate avoidance and also keep an eye on potential conflicts far ahead. The specified pair uses a short-range scale of about 3–4 miles and a long-range scale of about 12–16 miles, which covers both ends of typical traffic situations and supports timely decision‑making. Other option pairs don’t match this required combination of a clearly defined short-range and long-range scale, so they don’t meet the IMO requirement.