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Old 13-10-2010, 14:31   #1
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In Creating a Route on Charts, Do You Use True or Magnetic ?

Which do you use when manually plotting? True or Magnetic ?

I understand most use GPS, but if you know how to use paper charts to plot a route, which do you use true or magnetic?
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Old 13-10-2010, 14:35   #2
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Magnetic.

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Old 13-10-2010, 14:37   #3
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I always use magnetic for plotting a course on either paper or plotter. It removes the decision to remember which you used, as no doubt, at some stage, you will use a compass!
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Old 13-10-2010, 14:37   #4
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You can use either.... just be sure to remember which.....
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Old 13-10-2010, 14:39   #5
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Quote:
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You can use either.... just be sure to remember which.....
which is why I was asking what others use
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Old 13-10-2010, 14:42   #6
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I was taught to use magnetic, but to also denote that as magnetic by putting an M in front of the direction.
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Old 13-10-2010, 14:55   #7
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Quote:
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which is why I was asking what others use
BOTH... depends on where I'm sailing and calculations involved.. if its a strong tidal/coastal area I prefer True... I find it easier to do the sums...
but then I'm a pre GPS wrinkly... shoot we even learnt how to navigate with a needle n piece of string n old fashioned watch (pre-digital) and we ate REEL BREAD N BUTTER...
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Old 13-10-2010, 14:59   #8
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we ate REEL BUTTER...
Is that lube for your fishing gear?

Sorry, but couldn't resist.
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Old 13-10-2010, 15:04   #9
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Magnetic. A compass doesn't point to "True" (north).
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Old 13-10-2010, 15:10   #10
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I was formally taught that always its TRUE,

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Old 13-10-2010, 15:10   #11
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OK.. I didn't think I was crazy.. well a little.. but thats how I was taught (and how I plot) - magnetic..

But, for reasons I can't figure out, when I plot a route in my GPS (Lowrance HDS8), it plots it TRUE! I can't figure out how to show it as magnetic. I called lowrance, they couldn't figure it out either. Everything else in the GPS shows magnetic..'cept the route planner/list.

I plotted a course due (true) north, and it showed course 000 between the 2 waypoints! That is 17 degrees off of what my compass shows!!

Still waiting for a call back from Lowrance with an answer, or something. There initial reply was to just plot my paper courses in TRUE!! When I find a compass that shows true.. I could do that... but since my compass' show magnetic.. I need to use that!!

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Old 13-10-2010, 15:26   #12
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Important point to remember... Compasses can tell lies... paper charts can/do point out areas of magnetic variation/deviation in some areas, in others its unpredictable.. even more so if your torch/GPS/fancy all singing/dancing watch is close to it...
As for the Lowrance... well maybe the software man was an oldfashioned sailor...
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Old 13-10-2010, 16:14   #13
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A chart is drawn with true north as the defining base and any course line drawn on that chart will be relative to true north.
If you want to determine a course to steer from that course line, it needs to be converted to magnetic north to match your compass.
GPS should also be set to read magnetic north to match the compass.

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Old 13-10-2010, 16:22   #14
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Quote:
Originally Posted by spiritcat View Post
A chart is drawn with true north as the defining base and any course line drawn on that chart will be relative to true north.
If you want to determine a course to steer from that course line, it needs to be converted to magnetic north to match your compass.
GPS should also be set to read magnetic north to match the compass.

Peter
Yup. exactly. For some reason the route planner/editor only shows true (there is no function to change it to magnetic in the editor).. the rest of all the functions on the plotter do show magnetic.... Good thing I noticed it before following the gps route!
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Old 13-10-2010, 16:27   #15
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Quote:
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Important point to remember... Compasses can tell lies... paper charts can/do point out areas of magnetic variation/deviation in some areas, in others its unpredictable.. even more so if your torch/GPS/fancy all singing/dancing watch is close to it...
As for the Lowrance... well maybe the software man was an oldfashioned sailor...
true..which is why you should have your compass turned to account for deviation on board.. and the affects of mag variation on it as well.

When I was on the phone with lowrance.. once the tech got my question..there was dead silence..he got it! still havent heard from them about they plan on fixing it.. I just never heard of anyone following a true course on a boat..since so few compasses point true
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