Raymarine MARPA

[Ric]

Hello,

I'm in the process of buying a new Raymarine digital radar to replace my older Furuno 1622.

I have a couple of questions about MARPA:
1. Does it acquire targets automatically?
2. Does the alarm trigger if a target is projected to enter the guard ring? Or does the alarm only sound when the target actually enters the guard ring (as per my Furuno)?

 

[pvb]

Hello,

I'm in the process of buying a new Raymarine digital radar to replace my older Furuno 1622.

I have a couple of questions about MARPA:
1. Does it acquire targets automatically?
2. Does the alarm trigger if a target is projected to enter the guard ring? Or does the alarm only sound when the target actually enters the guard ring (as per my Furuno)?

It may depend slightly on which radar/plotter model you choose, but generally you have to manually select a target for MARPA tracking.

Raymarine products generally allow you to set a "safe radius" for MARPA targets, plus a "time to safe" period. A target will trigger a "dangerous" alarm if it is predicted to enter your safe zone within this time period.

For MARPA to work reasonably well, you need a rate gyro stabilised compass input.

 

[sailorman]

on a small boat yawing about its only a guide as to what might happen in calm flat water conditions.
in rough weather forget it

 

[homer]

On my C80, you have to select the targets manually. You then set the warning radius and get an alarm when the vessel enters that circle. You do get a guide from the targets projected vector if it is llikely to be a problem.

 

[Ric]

On my C80, you have to select the targets manually.

That's a bit disappointing. I was rather hoping it would automatically acquire any target that the radar picks up, then trigger an alarm if the target is predicted to get inside the guard ring.

 

[pvb]

That's a bit disappointing. I was rather hoping it would automatically acquire any target that the radar picks up, then trigger an alarm if the target is predicted to get inside the guard ring.

It can only process a maximum of 25 MARPA targets, which is one reason why they're manually selected.

 

[Ric]

It can only process a maximum of 25 MARPA targets, which is one reason why they're manually selected.

I wouldn't think it would be difficult to write an algorithm that could prioritise 25 targets a lot better than a human can.

 

[Tomahawk]

Manual target selection is necessary because a radar will not be able to differentiate betwen target A which is a headland and target B which is a ship..

We have one and I find it is very good... In reality you soon see which targets are not going to get near you and can discard them... Indeed once whan I crossed a TSZ with half a dozen ships going up then another half a dozen going down just as wqe had to popmthrough the lot... I was only tracking about three as the rest would not get anywhere near..

 

[Ric]

Why would it need to distinguish between a headland or a ship? Both are moving relative to the boat.

My primary need is for an alarm system that is a bit more sophisticated than a simple guard ring about the boat. Ideally I would like a system that can automatically acquire the nearest x targets (whether moving or stationary) and sound an alarm if MARPA predicts that any of them are going to get within a user-chosen distance within a user-chosen time. I would guess with the speed of modern processors on the latest multifunction displays, that this would be feasible.

Having to manually acquire a target lessens the potential usefulness of MARPA to me.

 

[lenseman]

I wouldn't think it would be difficult to write an algorithm that could prioritise 25 targets a lot better than a human can.

Urrm? It was standard equipment in the Andrew in the early 60's when I served.

The PPI would lock up on a target and FC or GD would loose a missile . . . job done. If the track stopped half way across the display, that target was history.

If the RN had it in the early 60's then it would be very easy to make for the leisure market 40 years down the road?

Ric, what you really needed to write was that you are not capable of writing the algorithm?


.

 

[oldbilbo]

The PPI would lock up on a target and FC or GD would loose a missile . . . job done. If the track stopped half way across the display, that target was history.

If the RN had it in the early 60's.....

I suspect that's what happened to a few of the target-towing Canberras we lost in the Portland Ranges last century....

 

[knuterikt]

ARPA with automatic target acquisition does exist

Furuno have a full ARPA on the the MFD8/MFD12 systems

ARPA that cant track 30 targets
Automatic & manual target acquisition
CPA/TCPA alarm
Two guard zones

Prizes has been dropping on theses units since the introduction of NavNet TZtouch