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13-10-2010, 14:31
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#1
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Registered User
Join Date: Aug 2010
Location: Boston, MA
Boat: 1968 Ohlson 38 Sloop
Posts: 1,063
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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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13-10-2010, 14:35
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#2
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Registered User
Join Date: Oct 2008
Location: Cruising the southern coast of Portugal and Spain
Boat: Leopard 40
Posts: 764
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Magnetic.
Maje
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13-10-2010, 14:37
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#3
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Registered User
Join Date: Aug 2009
Location: Queensland
Boat: Peterson 46
Posts: 340
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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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13-10-2010, 14:37
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#4
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Senior Cruiser
Join Date: Jan 2010
Location: PORTUGAL
Posts: 31,085
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You can use either.... just be sure to remember which.....
__________________
You can't oppress a people for over 75 years and have them say.. "I Love You.. ".
"It is better to die standing proud, than to live a lifetime on ones knees.."
Self Defence is no excuse for Genocide...
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13-10-2010, 14:39
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#5
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Registered User
Join Date: Aug 2010
Location: Boston, MA
Boat: 1968 Ohlson 38 Sloop
Posts: 1,063
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Quote:
Originally Posted by boatman61
You can use either.... just be sure to remember which.....
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which is why I was asking what others use
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13-10-2010, 14:42
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#6
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Registered User
Join Date: Oct 2010
Location: Marathon, FL
Boat: Hans Christian 33
Posts: 652
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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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13-10-2010, 14:55
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#7
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Senior Cruiser
Join Date: Jan 2010
Location: PORTUGAL
Posts: 31,085
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Quote:
Originally Posted by phantomracer
which is why I was asking what others use
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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...
__________________
You can't oppress a people for over 75 years and have them say.. "I Love You.. ".
"It is better to die standing proud, than to live a lifetime on ones knees.."
Self Defence is no excuse for Genocide...
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13-10-2010, 14:59
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#8
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Registered User
Join Date: Oct 2010
Location: Marathon, FL
Boat: Hans Christian 33
Posts: 652
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Quote:
Originally Posted by boatman61
we ate REEL BUTTER...
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Is that lube for your fishing gear? 
Sorry, but couldn't resist.
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13-10-2010, 15:04
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#9
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Registered User
Join Date: Mar 2006
Location: Tampa Bay area, USA
Boat: Beneteau First 42
Posts: 3,961
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Magnetic. A compass doesn't point to "True" (north).
__________________
"It is not so much for its beauty that the Sea makes a claim upon men's hearts, as for that subtle something, that quality of air, that emanation from the waves, that so wonderfully renews a weary spirit."
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13-10-2010, 15:10
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#10
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Nearly an old salt
Join Date: Jun 2009
Location: Lefkas Marina ,Greece
Boat: Bavaria 36
Posts: 22,801
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I was formally taught that always its TRUE,
dave
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13-10-2010, 15:10
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#11
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Registered User
Join Date: Aug 2010
Location: Boston, MA
Boat: 1968 Ohlson 38 Sloop
Posts: 1,063
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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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13-10-2010, 15:26
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#12
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Senior Cruiser
Join Date: Jan 2010
Location: PORTUGAL
Posts: 31,085
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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...
__________________
You can't oppress a people for over 75 years and have them say.. "I Love You.. ".
"It is better to die standing proud, than to live a lifetime on ones knees.."
Self Defence is no excuse for Genocide...
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13-10-2010, 16:14
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#13
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Registered User
Join Date: Sep 2008
Location: Hervey Bay, Queensland
Boat: Spirited 380 Catamaran
Posts: 91
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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.
Peter
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13-10-2010, 16:22
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#14
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Registered User
Join Date: Aug 2010
Location: Boston, MA
Boat: 1968 Ohlson 38 Sloop
Posts: 1,063
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Quote:
Originally Posted by spiritcat
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
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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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13-10-2010, 16:27
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#15
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Registered User
Join Date: Aug 2010
Location: Boston, MA
Boat: 1968 Ohlson 38 Sloop
Posts: 1,063
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Quote:
Originally Posted by boatman61
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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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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