View Poll Results: When using Radar, how often do you use ARPA/MARPA
I never use ARPA/MARPA, or I don't know what it is 12 31.58%
I occationally use ARPA/MARPA 17 44.74%
I use ARPA/MARPA on a regular basis 9 23.68%
Voters: 38. You may not vote on this poll

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Old 11-11-2014, 03:32 PM   #21
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Quote:
Originally Posted by Marin View Post
Our Furuno NavNet VX2 does not have ARPA but it does let you keep manual track of the bearing and range to two targets simultaneously. We have used this feature occasionally when boating in fog.
Furuno has a kit, ARP 11, usually sold in a kit with the PGR 500 heading sensor that adapts the 10.4" and Blackbox Vx2 to ARPA.
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Old 11-11-2014, 07:53 PM   #22
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Originally Posted by timjet View Post
I use MARPA to check speed on other boats especially in no wake zones

I have found the speed read out to be very inaccurate even on my new digital radar and heading sensor.
What Radar do you have that gives inaccurate speed readings?
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Old 11-11-2014, 08:14 PM   #23
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Originally Posted by twistedtree View Post
What Radar do you have that gives inaccurate speed readings?
I have a Raymarine E90W plotter and a Ray HD digital closed array radar. I was told at the time I installed the above equipment the MARPA function may not be accurate due to an older heading sensor. I had to replace the heading sensor earlier this year with the most current and noticed no improvement in MARPA function. The speed of a target can be off as much as 10 kts and the target heading though more accurate will be off especially if the target is traveling slow.
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Old 11-11-2014, 08:18 PM   #24
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I'm one of the people who voted "on a regular basis", but that doesn't mean I track every passing boat. It just means that I regularly find situations where it's useful.

At night is an obvious one. So are low visibility situations like fog.

But I have found many clear visibility situations where I find it very helpful. I've been in plenty of situations where I am on some sort of intersecting path with another boat. Of course if they have AIS that will tell you all you need, but many boats don't have AIS, and lots seem to think all they need is a receiver, but that's another discussion. Anyway, getting a MARPA lock lets you easily sort out how much of a collision course you are on, and monitor the situation through a safe pass.

I have also had situations where I'm working my way through a fleet of fishing boats with gear out running a depth contour. A MARPA lock makes it much easier to see where you are clear and where you need to make a course adjustment to stay clear. Maybe others can judge all this visually at a long distance, but I can't at the sort of distance that I like to keep from other boats. MARPA lets me do that.

Even on the ICW I have found great use for MARPA. I have encountered other boats that I am overtaking or that are overtaking me, and a MARPA lock lets me see how fast they are going. With that, I can figure out where we will pass and be sure it's a safe location, or adjust speed to cause it to be a safe location. I recall one particular case of this on the St Lawrence (not the ICW) where we were being overtaken by a freighter while passing through a particularly narrow and windy section. By knowing it's speed we were able to figure out where the pass would occur and see that we would be past the narrow section in into an open area. It took a lot of stress out of the next 45 minutes.
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Old 11-11-2014, 11:30 PM   #25
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I've only had radar (and MARPA) on charters but I focused on using it immediately. I downloaded the manuals in advance so I'd know how. Really enjoyed learning about it.
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