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Old 10-15-2014, 10:31 AM   #1
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Calling Simrad Radar Owners...

Calling all Simrad Radar owners. I've got some time on my Simrad package now and am having some troubling problems with the radar and am wondering if others are seeing the same issues.

1) Probably the most troubling is that MARPA works poorly. To best illustrate the problem, I picked out a boat with AIS, then also locked onto it as a MARPA target. Within some margin of error the AIS course/speed predictor on MARPA should match the AIS course/speed line. It doesn't, but is instead off by 10-20 degrees. I have also verified this against the trail of dots that the radar leaves showing the path of the boat, and against the course of boats in controlled shipping lanes where their course is both known and constant.

2) The MARPA course/speed predictor bounces all over the place the more movement there is in by boat. It's like it's not compensating for my boat's movement even though I have heave, pitch, and roll sensors in the Sat compass

3) The CU (course up) setting does not work. The radar can be set to HU, CU, or NU. When set to CU, the radar shows "CU" on the display, but continues to orient the display and compass rose based on the heading, not the COG. In cross current, this can be a big difference and further confuses the whole issue of the course predictor lines and what they mean.

By way of a little more background, and to answer what I'm sure will be the first wave of questions, here's some more info.

- I have two Simrad Radars on the boat. One is a 10KW open array, and the other is 4G. I get the same behavior from both radars.

- Both radars report that they have a valid heading source and the MARPA status is good.

- I have two different heading sources and have tried both with the same results. One is an HS70 Sat Compass that is a combination GPS and heading sensor and is supposed to be the ultimate in heading accuracy. It also reports pitch, roll, heave, etc. As backup I have a regular GPS and an RC42 rate compass. It's easy to switch between the two, and I get the same results both ways. I have also completely disconnected the HS70 to no avail.

- Display of the radar info is via a Simrad NSO black box running the latest SW. All components in the system have been updated to the vendors latest release.

Anybody else using MARPA and how does it work?
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Old 10-15-2014, 12:32 PM   #2
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We have a Simrad 4G unit tied into a Simrad NSE12 MFD. Not sure what the heading sensor is as it just got changed out before I left the boat a couple of weeks ago.

So far I've only played with the MARPA at the dock, and that was behind a breakwater, so I have no real understanding of how well it works. The heading sensor was not the correct one as well.

Once I'm back on board in a few weeks I will be looking closely at the MARPA so will let you know what I find. I'll be doing a variety of calibration runs with the tech to calibrate the new sensor, and now that you have mentioned it, will also check the MARPA performance.
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Old 10-15-2014, 12:45 PM   #3
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It still sounds like a heading sensor issue. What does simrad say?
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Old 10-15-2014, 01:02 PM   #4
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I just installed a NSS12, 4G radar, and RC42 a few weeks ago.

No experience with MARPA yet, but I'm going to do some real testing of the new unit this Saturday. Will let you know what I find out.

I do now the COG vector for my boat is not accurate, even after doing the automatic calibration of the RC42. It's consistently off about 10 degrees. The radar overlay aligns properly, though.

I've also had problems with the MFD not seeing the radar intermittently. A new radar interface box RI10 should be in today's mail, so I'll swap that out and see if the situation improves. If not, I'll move on to other components since we've ruled out any software glitches.
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Old 10-15-2014, 03:49 PM   #5
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Quote:
Originally Posted by Capt.Bill11 View Post
It still sounds like a heading sensor issue. What does simrad say?
That was Simrad's first response, but I have two different sensors, both of which agree with each other within a degree or two, and both yield the same results. I have also checked the radar image alignment with a land mass on the chart plotter which is a good way to check your heading sensor alignment. The radar image overlays perfectly, which I think confirms that the heading is accurate. So if there is an error, it's exists with and is the same error on both heading sensors, or it's a problem that I can't spot.

I have subsequently posted a handful of videos showing all this for Simrad to examine, but they have not accessed them yet.
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Old 10-15-2014, 03:57 PM   #6
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Quote:
Originally Posted by Retriever View Post
I do now the COG vector for my boat is not accurate, even after doing the automatic calibration of the RC42. It's consistently off about 10 degrees. The radar overlay aligns properly, though
To the extent I understand this stuff, and I'm learning more every day, COG comes from your GPS, not the heading sensor. HDG (heading) comes form the heading sensor. Often they are the same, but not always. Two cases come to mind.

1) When the boat isn't moving, your GPS can't tell what direction you are heading. It needs movement, then connects the dots to figure your direction. So COG from a GPS will be trash if you are not moving.

2) Your HDG will tell you what direction the boat is pointing, even when it's not moving, but that's not always the same as the direction the boat is moving. Consider a strong side current where the boat will be pointing one direction, but cumulative movement (COG) will be different because of the current.
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Old 10-15-2014, 04:06 PM   #7
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Quote:
Originally Posted by twistedtree View Post
To the extent I understand this stuff, and I'm learning more every day, COG comes from your GPS, not the heading sensor. HDG (heading) comes form the heading sensor. Often they are the same, but not always. Two cases come to mind.

1) When the boat isn't moving, your GPS can't tell what direction you are heading. It needs movement, then connects the dots to figure your direction. So COG from a GPS will be trash if you are not moving.

2) Your HDG will tell you what direction the boat is pointing, even when it's not moving, but that's not always the same as the direction the boat is moving. Consider a strong side current where the boat will be pointing one direction, but cumulative movement (COG) will be different because of the current.
Almost every time I use the boat I cross Rosario Strait perpendicular to the current, which can run to a couple knots. Having the COG vector rather than the heading vector allows me to set an appropriate course that takes into account the cross current.

It makes sense HDG would come from the heading sensor (and the heading vector is working properly) and COG would come from GPS.

But I think there's something going on in the Simrad software that's causing a problem with the COG info. The laptop running Coastal Explorer, the iPad running iNavX, and the NSS12 are all getting GPS data from the same source (Vesper XB8000). The iPad and the CE on the laptop show the correct COG vector but the GPS doesn't.

Prior to installing the heading sensor the COG vector on the Simrad was, I think, displaying correctly. This weekend I'll disconnect the heading sensor and see if that impacts the COG vector.

Is your COG vector showing up accurately? Sorry to sidetrack your thread, but perhaps these issues are related...
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Old 10-15-2014, 04:33 PM   #8
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No distraction at all. It's all related. If your issue started when the heading sensor was added, then my first guess would be that your chart plotter is set to show heading rather than course. You can select eitheradn it determines what teh little arrow coming off the bow of your boat means.. I thing it's Menu, Settings, Units and you can select between course and heading.
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