ARPA

Acronym for Automatic >Radar Plotting Aid. A marine >Radar with automatic >Radar plotting aid (ARPA) capability can create tracks using >Radar contacts. An alarm will go if some of the ARPA objects are on a collision Course with the Ship. The system can calculate the tracked object's Course, speed and >Closest Point of Approach (CPA), thereby knowing if there is a danger of collision with the other Ship or landmass that is within >Radar Range.