The International Maritime Consultative Organization (now IMO) carriage requirement for ARPA began to take effect in 1984 and became progressively mandatory worldwide; prior to this, for certain classes of vessels trading to the USA, a national requirement was introduced in 1982. These radar plotting aids perhaps constituted the first widespread use of computing power aboard merchant vessels. In implementation, even the early ARPAS were much more than the mere plotting aid which their name suggests. Sophisticated processing gave the navigator a system which offered significant assistance in scenario analysis, with the well known ability to display graphically the effect of a trial manoeuvre being the most active element of the system.

Radar and ARPA are used both for anti-collision purposes and for navigational purposes. The requirements for ‘ground-stabilization for navigation’ and ‘sea-stabilization for collision-avoidance’ seem to exclude each other. Since the development of True Motion radar (TM), there is the need for an input of Own Ship's velocity. Since then, the mode of velocity input and, consequently, the mode of stabilization have been the subject of controversy. The problem became even more important by the introduction of ARPA, by the use of video map overlays and by the introduction of complex integrated navigation systems including radar.

Ships' bridge watchkeeping, although the prime task of the officer of the watch, makes very low task demands in terms of information processing and required speed of response compared to most other vigilance tasks. Consequently, performance of the visual lookout task is difficult to describe and evaluate systematically. Results from an on-board observational study show that lookout lapse periods can be economically described by simple mathematical models, which assist in comparison and evaluation of task performance.