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been playing around with my chartplotter, and comparing with the paper chart working out bearings and distances to inshore wrecks

do i keep the chartplotter (bearings true)or(magnectic)as you can switch between the two, when using the compass and plotter together going to a waypoint whats the right combination thanks
 

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Your actual paper charts always show true north and you work out the compass variation based on the info given on that chart, so many minutes or seconds east or west per annum.

If you work direct from the chart without having calculated magnetic variation first then ( never having thought on the point before ) I`d say keep your plotter on true. ( I await to be shot down in flames with bated breath)

Me with the bated breath, not the flames :crazy: God I`m bored.
 

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I think you should be Magnetic, as your compass is about 3.5 degrees off to the west. I would not put all my trust into a GPS. They are there only to back up Paper Charts
 

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Are working from satellite signals, how can they be given as "true" readings? surely the signal would be given as relative to their position to the poles, & would therefore be magnetic?
Dont tell me I have to start putting annual magnetic deviations into my chartplotter waypoints, & how is it that fixed position waypoints such as bouys, appear on my chartplotter, at exactly the same place as they do on the chart? I am confused.com? Sharpshooter! shut your face!:nono:
blueskip
 

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Are working from satellite signals, how can they be given as "true" readings? surely the signal would be given as relative to their position to the poles, & would therefore be magnetic?
Dont tell me I have to start putting annual magnetic deviations into my chartplotter waypoints, & how is it that fixed position waypoints such as bouys, appear on my chartplotter, at exactly the same place as they do on the chart? I am confused.com? Sharpshooter! shut your face!:nono:
blueskip
A compass is affected by magnetic variation,i don't think a satellite is,surely all gps bearings are true.
 

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A compass is affected by magnetic variation,i don't think a satellite is,surely all gps bearings are true.
they maybe but you have the option to have them read magnetic, and would therefore correspond with your compass. I am no Marko Polo but surely it makes sense to have them both doing the same. That way your compass heading would be roughly in line with your proposed track.
 

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they maybe but you have the option to have them read magnetic, and would therefore correspond with your compass. I am no Marko Polo but surely it makes sense to have them both doing the same. That way your compass heading would be roughly in line with your proposed track.
You're probably right but to be honest i rarely use a compass these days.
 

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I think you should be Magnetic, as your compass is about 3.5 degrees off to the west. I would not put all my trust into a GPS. They are there only to back up Paper Charts
I agree that the GPS is a back up but if I put my protractor onto my paper chart it will give me a true course. The variation adjustment is only to convert back the inaccurate reading from my magnetic compass.
 

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I'm sorry, anyone who pontificates that "your gps is only a back up to your charts and compass" is a doddering buffoon. 99.9% of commercial shipping is using gps input to a C-Map chart machine or similar. Charts are kept but only as last resort back up. I've just come down from the bridge right now and not one officer was polishing his sextant!

I'm not saying don't know how to use them, but true North on a GPS will be fine, but do carry a compass.
 

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I'm sorry, anyone who pontificates that "your gps is only a back up to your charts and compass" is a doddering buffoon. 99.9% of commercial shipping is using gps input to a C-Map chart machine or similar. Charts are kept but only as last resort back up. I've just come down from the bridge right now and not one officer was polishing his sextant!

I'm not saying don't know how to use them, but true North on a GPS will be fine, but do carry a compass.
Is that why you keep banging into one another???
 
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they maybe but you have the option to have them read magnetic, and would therefore correspond with your compass. I am no Marko Polo but surely it makes sense to have them both doing the same. That way your compass heading would be roughly in line with your proposed track.
I still use my compass, especialy when positioning or coming up to a mark, you often dont have a referance, so my way, is compass and heading. I'm with Aquabell, if my GPS goes down I'm on compass and chart, its reasuring to be using magnetic as a standard, you have the option with GPS to automaticaly use magnetic.

Its what you get used to I supose? ET's OPO
 

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they maybe but you have the option to have them read magnetic, and would therefore correspond with your compass. I am no Marko Polo but surely it makes sense to have them both doing the same. That way your compass heading would be roughly in line with your proposed track.
As has been said, whatever method suits you best. If the GPS is set to magnetic, fine, it will, "in theory" read the same as your compass but only on certain headings. The compass should be accompanied by a deviation card which shows how far off magnetic it is reading at various points as a result of on board deviation, gas bottles, other metallic objects, certain other electronics, a large area of steel bolts nearby etc etc. Any one of them will cause compass deviation as opposed to magnetic variation. On steel boats or boats with lots of steelwork it can be surprising how much the compass can be affected by deviation, up to as much as 60 or 90 degrees in extreme cases. Other option to overcome that is a fluxgate compass.

How you can plumb the deviation into your gps I have no idea, doubt if you can. That then means your compass and gps on magnetic will read different , more often than they correspond.

A bit like a stopped clock. Perfectly accurate twice a day but a chocolate fireguard the rest.
 

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Is that why you keep banging into one another???
I spend my time avoiding other ships, and have some others to help me. I'm towing 50 million dollars worth of electronics around. 1 km wide 6 km long - it makes the north Sea seem crowded.

Every point on the gear is positioned to <3m, and none of it uses a magnetic compass.
 
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Having my doubts which way best?? especialy as I have to get into this a bit deeper, setting up the radar soon??:whistling

ET
 

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I spend my time avoiding other ships, and have some others to help me. I'm towing 50 million dollars worth of electronics around. 1 km wide 6 km long - it makes the north Sea seem crowded.

Every point on the gear is positioned to <3m, and none of it uses a magnetic compass.
And when you get to shoal waters you stop and wait for a pilot, we do not have that luxury, so who are the buffoons?
 
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