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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.
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.
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.
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.”