Automatic Radar Plotting Aids (ARPA) Practice Test

Steady state tracking in ARPA requires both ships to maintain speed and course to ensure that the future positions of the target can be accurately predicted. When both the observer (the ship equipped with ARPA) and the target ship are at constant speeds and following steady courses, the ARPA system can reliably calculate the target's various parameters, such as range and relative motion. This stability enables effective tracking of the target's trajectory and helps in collision avoidance decisions.

If either vessel changes its speed or course, the predictive accuracy of the ARPA system can be compromised, leading to an unreliable tracking situation. In contrast, if one vessel slows down or alters course while the other remains constant, the calculated positions can show irregularities, which may hinder navigation safety. For these reasons, maintaining consistent speeds and courses for both vessels is crucial in achieving steady state tracking in ARPA systems.