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A marine radar with automatic radar plotting aid (ARPA) capability can create tracks using radar contacts. 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. Development of ARPA started after the accident when the Italian liner SS Andrea Doria collided in dense fog and sank off the east coast of the United States. ARPA radars started to emerge in the 1960s and, with the development of microelectronics. The first commercially available ARPA was delivered to the cargo liner MV Taimyr in 1969〔(【引用サイトリンク】 publisher = Kongsberg Maritime )〕 and was manufactured by Norcontrol, now a part of Kongsberg Maritime. ARPA-enabled radars are now available even for small yachts. ==History== The availability of low cost microprocessors and the development of advanced computer technology during the 1970s and 1980s have made it possible to apply computer techniques to improve commercial marine radar systems. Radar manufactures used this technology to create the Automatic Radar Plotting Aids. ARPAs are computer assisted radar data processing systems which generate predictive vectors and other ship movement information. The International Maritime Organization (IMO) has set out certain standards amending the International Convention for the Safety of Life at Sea requirements regarding the carrying of suitable automated radar plotting aids. The primary function of ARPAs can be summarized in the statement found under the IMO Performance Standards. It states a requirement of ARPAs: "to improve the standard of collision avoidance at sea: Reduce the workload of observers by enabling them to automatically obtain information so that they can perform as well with multiple targets as they can by manually plotting a single target". As we can see from this statement the principal advantages of ARPA are a reduction in the workload of bridge personnel and fuller and quicker information on selected targets. A typical ARPA gives a presentation of the current situation and uses computer technology to predict future situations. An ARPA assesses the risk of collision, and enables operator to see proposed maneuvers by own ship. While many different models of ARPAs are available on the market, the following functions are usually provided: # True or relative motion radar presentation. # Automatic acquisition of targets plus manual acquisition. # Digital read-out of acquired targets which provides course, speed, range, bearing, closest point of approach (CPA, and time to CPA (TCPA). # The ability to display collision assessment information directly on the Plan Position Indicator (PPI), using vectors (true or relative) or a graphical Predicted Area of Danger (PAD) display. # The ability to perform trial maneuvers, including course changes, speed changes, and combined course/speed changes. # Automatic ground stabilization for navigation purposes. ARPA processes radar information much more rapidly than conventional radar but is still subject to the same limitations. ARPA data is only as accurate as the data that comes from inputs such as the gyro and speed log. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Automatic radar plotting aid」の詳細全文を読む スポンサード リンク
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