Marine Glossary

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ARPA

Automatic Radar Plotting Aid. A computerized function of modern radars that can track, determine, and analyze interaction data for vessel targets on the radar screen. Such data might include CPA, time to CPA, true course and speed, relative course and speed, and so on. Targets being tracked typically show a vector of projected motion. The term “ARPA” is often considered to be restricted to systems that meet the standards of the IMO, whereas other implementations of this functionality use modifications of the name. ARPA-enabled units require a heading sensor and some require an optional ARPA plug-in card. On small-craft radar this function is often referred to as "mini-ARPA," "ARP," or some other slight variation of the name to distinguish it from the certified IMO standards, which are not always pertinent to small-craft installations.