Radar Feature: MARPA Targets


Last Updated on September 10, 2019 by Amy

Our AIS (Automatic Identification System) is one of our favorite electronics on the boat.  It helps us make better navigational decisions, especially in high traffic areas or ship channels.  However, while cruising through South East Asia, we encountered a lot of fishing boats that did not have AIS onboard.  That’s when the MARPA feature on radar comes in handy!

In fact, we’re surprised by how many cruisers are out here who don’t know that you can track radar targets like you would an AIS target.

What is MARPA?

MARPA stands for Mini-Automatic Radar Plotting Aid.  Using MARPA, you can manually identify radar targets for tracking.  A full ARPA will automatically track radar targets, but most cruising boats aren’t going to have ARPA.

Why Should you Track MARPA Targets?

Just like with AIS, a MARPA target will tell you the speed and direction of the boat.  It will also tell you CPA (Closest Point of Approach) and TCPA (Time to Closest Point of Approach).  Alarms will sound if the CPA is within your tolerances.  An alarm will also sound if the target disappears.

How to Track MARPA Targets

I visually identified a radar target on my port side.
I clicked on the target and a menu popped up. At the bottom, I selected “Acquire Target”.
At first, the chartplotter reads 0°0 and 0 knots. It takes a few minutes to acquire the target.
The target has been identified and now shows a course of 11° true at 5.2 knots.
To cancel the target, I clicked on the radar signature again and selected “Cancel Target” from the menu.

About Our Radar

Our radar is a Raymarine RD418HD:

“Raymarine RD418HD Color Radome. HD Color Radomes are ideal when power is at a premium and mounting space is limited or restricted by rigging, excellent for sailboats, RIBs and smaller powerboats.  Raymarine’s HD Color radome scanners combine the power and clarity of HD Color signal processing with an ultra-compact scanner suitable for all types of vessels.”

Did you know you could track targets like this?  What other radar features do you find helpful?

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  1. Thanks for the explanation Amy. Here I was thinking MARPA was something like DARPA. Myself, being a software designer, read; “talk with any Raymarine MFD running the LightHouse 3 operating system” and thought “Now that is cool!”.

    Of course, they meant on your vessel while I was thinking one could see the other persons radar image, what they were seeing, like a Mesh router, now that would be a game changer!

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