Mini-automatic radar plotting aid
Mini-automatic radar plotting aid (or MARPA) is a maritime radar feature for target tracking and collision avoidance. Targets must be manually selected, but are then tracked automatically, including range, bearing, target speed, target direction (course), CPA (closest point of approach), and TCPA (time of closest point of approach), safe or dangerous indication, and proximity alarm.
Source: Wikipedia — Mini-automatic radar plotting aid (CC BY-SA 4.0)