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Evolution of ARPA in Marine Radar

Automatic Radar Plotting Aid (ARPA) systems were developed after a ship collision to help calculate tracked objects' course, speed, and risk of collision. The first commercial ARPA was delivered in 1969. Developments in microelectronics allowed ARPA to be integrated into radar systems. Initially, ARPA units were standalone but are now integral, combining radar and computer processing for easier comparison of data. Raster-scan displays gradually replaced radial-scan displays, making it easier to present auxiliary information to users.

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431 views4 pages

Evolution of ARPA in Marine Radar

Automatic Radar Plotting Aid (ARPA) systems were developed after a ship collision to help calculate tracked objects' course, speed, and risk of collision. The first commercial ARPA was delivered in 1969. Developments in microelectronics allowed ARPA to be integrated into radar systems. Initially, ARPA units were standalone but are now integral, combining radar and computer processing for easier comparison of data. Raster-scan displays gradually replaced radial-scan displays, making it easier to present auxiliary information to users.

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Adrian
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Vasile Radu Adrian

ET32

Automatic Radar Plotting Aid (ARPA)

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 and was manufactured by
Norcontrol, now a part of Kongsberg Maritime. ARPA-enabled radars are now available even for
small yachts.

Vasile Radu Adrian


ET32

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.

Standalone and integral ARPAs


Over the past 10 years, the most significant changes to the ARPA systems have been in
their design. The majority of ARPAs manufactured today integrate the ARPA features with the
radar display.

Vasile Radu Adrian


ET32
The initial development and design of ARPAs were stand-alone units. That is because
they were designed to be an addition to the conventional radar unit. All of the ARPA functions
were installed on board as a separate unit but needed to interfaced with existing equipment to get
the basic radar data. The primary benefits were cost and time savings. This of course was not the
most ideal situation and eventually it was the integral ARPA that replaced the stand-alone unit.
The modern integral ARPA combines the conventional radar data with the computer data
processing systems into one unit. The main operational advantage is that both the radar and
ARPA data are readily comparable.

ARPA displays
From the time radar was first introduced to the present day the radar picture has been
presented on the screen of a cathode ray tube. Although the cathode ray tube has retained its
function over the years, the way in which the picture is presented has changed considerably.
From about the mid-1980s the first raster-scan displays appeared. The radial-scan PPI was
replaced by a raster-scan PPI generated on a television type of display. The integral ARPA and
conventional radar units with a raster-scan display will gradually replace the radial-scan radar
sets.

Raster-scan PPI
The IMO Performance Standards for radar to provide a plan display with an effective
display diameter of 180mm, 250mm, or 340mm depending upon the gross tonnage of the vessel.
With the diameter parameters already chosen, the manufacturer has then to decide how to
arrange the placement of the digital numerical data and control status indicators. The raster-scan
display makes it easier for design engineers in the way auxiliary data can be written.

Vasile Radu Adrian


ET32

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