ARPA/MARPA

[steverow]

Does anyone know what the differences are in NMEA sentence implementation between ARPA and MARPA....is MARPA just a seatalk thing only?

Steve.

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[pandroid]

I wasnt aware that NMEA and MARPA were related. MARPA is simply Raymarine's version of ARPA, with the 'M' standing for 'Mini' but really meaning 'Manual' - as, unlike full ARPA you have to identify the target yourselves before the system will track it.

The MARPA systems need a high resolution compass input (10 pps) to have any kind of accuracy and Seatalk (Raymarine's proprietry bus) can only manage 2pps, hence the emergence of the 'Smart Heading Sensor' which is a gyro unit to stabilise the compass input and provide it at high frequency.

Personally, for a yacht, I'm not sure the SHS is worth it. I've tried the system with and without it and cant tell the difference (its not that great with either).

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[steverow]

What I am after is the NMEA sentences that ARPA sends....is it just TTM (tracked target marker) or is there more to it than that?
I need to know the sentences that a ARPA or MARPA enabled radar will be sending to an ARPA enabled plotter such as CM93.
Steve.

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[pvb]

Raymarine sends...

Raymarine kit outputs TTM via NMEA.

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[chrisb]

without shs only functions in calm conditions. shs essential. superb system.sailed to coruna without the shs and back withit i certainly noticed the difference.

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