What is Automatic Radar Plotting Aid (ARPA)?

Automatic Radar Plotting Aid (ARPA) is a sophisticated marine radar system designed to enhance navigational safety by automatically plotting the positions of targets and predicting their future movements.

By providing real-time data on the speed, course, and position of other vessels, ARPA significantly reduces the workload on navigators and improves situational awareness, especially in congested or restricted waters.

The development of ARPA was driven by the need to improve maritime safety and efficiency. Traditional radar systems required manual plotting of targets, which was time-consuming and prone to human error.

The advent of digital technology in the late 20th century allowed for the automation of this process, leading to the development of ARPA systems. These systems were designed to automatically track targets, analyze their movements, and provide valuable collision avoidance 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 function 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.

ARPA tracks the following parameters and has the following functionalities:

1.Motion Radar Presentation

True and Relative Motion Display: Capable of presenting both true and relative motion radar information for enhanced situational awareness.

2.Target Acquisition

Automatic and Manual Acquisition: Supports both automatic and manual target acquisition to ensure comprehensive tracking of all relevant targets.

3.Digital Read-Out

Detailed Target Information: Provides digital read-outs for acquired targets, including:

Course
Speed
Range
Bearing
Closest Point of Approach (CPA)
Time to Closest Point of Approach (TCPA)
Bow Crossing Range and Time

4.Collision Assessment

Enhanced Display: Directly displays collision assessment information on the Plan Position Indicator (PPI), utilizing:

Vectors (true or relative)
Graphical Predicted Area of Danger (PAD) display

5.Trial Maneuvers

Simulation Capabilities: Enables the performance of trial maneuvers, including:

Course changes
Speed changes
Combined course and speed changes

6.Navigation Stabilization

Automatic Ground Stabilization: Offers automatic ground stabilization for precise navigation purposes.

7.Rapid Processing

Enhanced Processing Speed: Processes radar information much more rapidly than conventional radar systems, though it remains subject to the same limitations.

8.Data Accuracy

Dependence on Input Accuracy: ARPA data accuracy is contingent on the precision of input data from sources such as the gyro and speed log.

ARPA

Difference between RADAR and ARPA

Feature	Radar	ARPA (Automatic Radar Plotting Aid)
Alerts and Alarms	Limited	Provides visual and audible collision risk alerts
Automation	Manual plotting required	Automatic plotting and tracking
Collision Avoidance	Basic visual information	Provides detailed collision avoidance information
Data Display	Real-time display of echoes on the screen	Enhanced display with target vectors, CPA, TCPA, and trails
Ease of Use	Requires constant monitoring and manual plotting	User-friendly interface with automated functions
Predictive Capabilities	None	Predicts future positions and movements of targets
Primary Function	Detects and displays the position of objects	Detects, tracks, and predicts the movement of objects
Target Identification	Limited, relies on visual identification	Can integrate with AIS for detailed target information
Target Tracking	Limited to manual observation	Automatically tracks multiple targets simultaneously
Vector Display	Not available	Shows true and relative vectors of targets

In conclusion, the Automatic Radar Plotting Aid (ARPA) is a a transformative tool in maritime navigation, fundamentally enhancing safety and operational efficiency.

By automating the tracking of other vessels and predicting their movements, ARPA tries to resolve the problems faced by bridge crews, providing them with crucial information at a glance—an invaluable asset in busy and complex waters.

The advancements in digital technology have allowed ARPA to replace the manual plotting of radar targets, significantly reducing the risk of human error and streamlining navigational processes.

With features that display real-time data on speed, course, and distance to potential collisions, ARPA not only assists in immediate decision-making but also enables crews to run simulations for various navigational scenarios.

The framework established by the International Maritime Organization (IMO) underscores the vital role ARPA plays in enhancing maritime safety. By equipping bridge teams with the tools for smarter and quicker decision-making, it empowers them to monitor multiple vessels with reduced effort.

About Author

Karthik, a former navigating officer now turned into a maritime tech innovator focused on advancing the shipping industry through digital transformation. As the co-founder of MarineGPT and a product leader at Marine Insight, he develops AI-driven solutions and tech tools to make knowledge accessible to maritime professionals worldwide.

Disclaimer :
The information contained in this website is for general information purposes only. While we endeavour to keep the information up to date and correct, we make no representations or warranties of any kind, express or implied, about the completeness, accuracy, reliability, suitability or availability with respect to the website or the information, products, services, or related graphics contained on the website for any purpose. Any reliance you place on such information is therefore strictly at your own risk.

In no event will we be liable for any loss or damage including without limitation, indirect or consequential loss or damage, or any loss or damage whatsoever arising from loss of data or profits arising out of, or in connection with, the use of this website.