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KVH Azimuth and Furuno Navnet magnetic variation

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KVH Azimuth and Furuno Navnet magnetic variation

Old 07-13-2012, 11:39 AM
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Default KVH Azimuth and Furuno Navnet magnetic variation

I just got my Azimuth 1000 back from KVH for repair and on the repair invoice it stated that the compass is magnetic north and that the GPS chartplotter was True north and that I had to configure the magnetic variation for the KVH and Furuno to play nice together. I have my Furuno configured to use magnetic and not true compass bearings so I thought I was good to go but now I am wondering if I possibly have things not setup optimally? I trailer my boat all over the NE CT, RI, MA and the chartplotter always seems to be dead on but the KVH always seemed to conflict a little with the Furuno. I just thought it was the update interval but maybe not. Do I have to configure magnetic variation on either my Furuno or the KVH Azimuth 1000 in order to have good reliable heading information displayed on the plotter? If so what would the variation be for the NE? Thanks!
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Old 07-18-2012, 08:17 AM
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No help here? I thought for sure someone would have some experience with this issue.
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Old 07-18-2012, 05:44 PM
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Default KVH Compass

Do you calibrate the compass while on board to compensate for deviation on your boat. Mine was way off at first. While doing the rate compass calibration for the auto-pilot, the KVH read dead on. Meaning, it was also recalibrate.

I did have to move the rate compass to a lower location. It was too close to the KVH.

Give the KVH calibration a try.
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Old 07-19-2012, 06:24 AM
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This terminology is completely bolluxed thanks to the vendors.

Deviation is not the same thing as variation.

Variation is a difference in magnetic heading caused by shifts in the earths magentism at different geographic locations. It can be calculated using some very complex math, or you can get it from published charts for a specific area.

Deviation is error imposed by interference on your boat. Deviation will also vary based upon your heading; it is not a constant.

The difference between True North and Magnetic north is Variation.

The difference between Magnetic North and your compass heading is Deviation.

The difference between True North and Compass north is the sum of deviation and variation.

TVMDC

Your chartplotter can be set to display either True or Magnetic. But, what is magnetic in this use? Is it a heading based on variation? Or is it based on the compass heading? When it shows cog, is that magenetic or compass?

Your KVH is displaying compass north, NOT magnetic north.

Your KVH will (almost) never match a Magnetic course heading, and there is no setting you can adjust in your chartplotter to make it happen..

Makes my head hurt.

Last edited by gerg; 07-19-2012 at 07:45 AM.
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Old 07-20-2012, 06:55 AM
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Thanks Greg that definitely was a huge help indeed and exactly what I was looking for. So after I redo the KVH calibration how should I setup my chartplotter? True or magnetic as I am completely confused now with all of this compass stuff? What is the difference between CSE and Heading? I was under the mistaken assumption that they were somewhat one in the same? Just want to have accurate heading info fed from the KVH to my Furuno and I know that something isn't configured properly because they don't seem to jibe with each other. Thanks for your insight.
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Old 07-20-2012, 08:03 AM
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The two terms they seem to use are heading and bearing. Heading will come from your compass and be per standard compass. Bearing will be the Magnetic or True course you are following to some destination. They will also use COG, or course over ground, which is a bearing. CSE is course to waypoint, also a bearing.

If you have no compass connected to your chartplotter, and it calculates your course based on successive gps points, it will display bearing. In reality, your boat may be pointing an entirely different direction, which would be it's heading. You would see this if you were drifting for example, or if you had to crab into current/wind to maintain a course.

Bearing is what you would plot with on a paper chart.

Most chartplotting systems will display either or both (assuming you have an electronic compass connected). Generally speaking, if it diislplays either M or T after the degrees, it's a bearing. If they just display it in degrees, it's a heading.

Its really just preference which you use (M or T). Almost nobody uses paper charts anymore, but if they did it would be easier for them if you gave your bearing in T.
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Old 07-20-2012, 11:02 PM
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Well thanks again but I fear I am once again a bit confused???? My thinking is Heading (via the KVH fluxgate compass) and my course as shown on the chartplotter should be one in the same...Correct? On my Furuno it displays CSE, COG, BEARING on the top of the display while navigating to a waypoint. I also have another data box that I turn on that displays HEADING in degrees which comes from the KVH. Now I would expect some variation between my reported CSE (via GPS) and my reported heading (via KVH) because the two data points are calculated differently. But my heading displayed on the KVH and the heading displayed on my Furuno always seem to be off significantly although it is much better since I got back from them for repair. I still have to accomplish the ring around the rosey calibration to get it dead on but right out of the box from repair it gave me a very accurate heading value that jibed with my mechanical Ritchie compass sitting in the driveway. I guess I will have to do some additional reading up on all of this stuff as I thought I knew it well after taking the Capts. course but not using it every day tends to make the mind a little foggy.
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