ARPA stands for which system?

• A. Automatic Radar Processing Algorithm
• B. Automatic Route Planning Apparatus
• C. Automatic Radar Plotting Aid
• D. Automatic Radar Pilot Assistant

Answer: (C)

ARPA is an Automatic Radar Plotting Aid. This system automatically tracks multiple radar targets, calculating their relative bearing, range, course, and speed, and then predicts future positions to show where each target will be. It provides data like closest point of approach and time to closest point of approach, often with vectors and alerts to help you assess and avoid collisions. That automatic plotting and tracking function is what distinguishes ARPA from other phrases that aren’t standard names for this system. Automatic Radar Processing Algorithm would imply a generic processing method rather than the specific plotting and tracking capability ARPA provides; Automatic Route Planning Apparatus suggests route design rather than real-time collision avoidance; Automatic Radar Pilot Assistant isn’t the established term for this function. So the meaning that matches the system used on ships is Automatic Radar Plotting Aid.