I am new to this forum (first time) so please bare with me! When you are navigating do you rely on true North or navigate using the magnetic North bearing (sorry) because at the end of the day you are using the chart rose ( which sits according to magnetic North in your particular part of the world) and compass to steer your course.
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It depends
On short sails in local area, I use the magnetic compass rose on my chart. On longer cruises into unfamiliar waters, I use the GPS more so I use true north and convert to magnetic for the helm.
On short sails in local area, I use the magnetic compass rose on my chart. On longer cruises into unfamiliar waters, I use the GPS more so I use true north and convert to magnetic for the helm.
Most GPS units...
...have a setup option to set your unit to either true or magnetic north. I personally can see no advantage of using true north on your GPS and then converting it when you use your compass (which is obviously pointing to magnetic north). And most charts that I have, or have seen, have a compass rose that shows both true and magnetic. Once you have both your compass and GPS set to magnetic, I think you are good to go....
...have a setup option to set your unit to either true or magnetic north. I personally can see no advantage of using true north on your GPS and then converting it when you use your compass (which is obviously pointing to magnetic north). And most charts that I have, or have seen, have a compass rose that shows both true and magnetic. Once you have both your compass and GPS set to magnetic, I think you are good to go....
Navigation basics
Sounds like you would benefit from a basic navigation course... It is much easier all round to think in terms of True North. Most charts are oriented True North and all compass roses are oriented that way as well but have a magnetic rose inside the true rose to indicate the true values corrected to magnetic for the year that the chart was printed. Keep in mind that the variation in any given area will changes over the years dur to the magnetic north drift. The rate is marked on the magnetic rose with a + or - value so if you are using an old chart the varaition may be off a small amount. With your GPS (and radar if applicable) in true north mode the only conversion you would have to do is for your steering compass and any hand held magnetic compasses you may use to take fixes (if you don't have GPS). The easy conversion is T-V-M-D-C which stands for True - Variation - Magnetic - Deviation - Compass. An easy way to remember is "True Virgins Make Dull Company". (OK, it is sexist but an easy phrase to remember) Most people forget the deviation component but on long ocean voyages an error of a few degrees can add up. Deviation is the error caused by the megnetic anomalies in you boat near the compass. Most compasses have a set of corrector magnets that are use to minimize this error but it is useful to determine the errors in your setup and make up a deviation card for the main points of the compass so you can apply them according to the formula above. This is done by a compass swing and is best left to proffessionals to do. From True to Compass use the positive and negative values as indicated on the compass rose and your deviation table. From compass to true reverse the formula and the values. Hope this helps.
Sounds like you would benefit from a basic navigation course... It is much easier all round to think in terms of True North. Most charts are oriented True North and all compass roses are oriented that way as well but have a magnetic rose inside the true rose to indicate the true values corrected to magnetic for the year that the chart was printed. Keep in mind that the variation in any given area will changes over the years dur to the magnetic north drift. The rate is marked on the magnetic rose with a + or - value so if you are using an old chart the varaition may be off a small amount. With your GPS (and radar if applicable) in true north mode the only conversion you would have to do is for your steering compass and any hand held magnetic compasses you may use to take fixes (if you don't have GPS). The easy conversion is T-V-M-D-C which stands for True - Variation - Magnetic - Deviation - Compass. An easy way to remember is "True Virgins Make Dull Company". (OK, it is sexist but an easy phrase to remember) Most people forget the deviation component but on long ocean voyages an error of a few degrees can add up. Deviation is the error caused by the megnetic anomalies in you boat near the compass. Most compasses have a set of corrector magnets that are use to minimize this error but it is useful to determine the errors in your setup and make up a deviation card for the main points of the compass so you can apply them according to the formula above. This is done by a compass swing and is best left to proffessionals to do. From True to Compass use the positive and negative values as indicated on the compass rose and your deviation table. From compass to true reverse the formula and the values. Hope this helps.
Yes J-G but??
As the author wrote if you are sailing along and using just a chart and a compass forget about your GPS showing true North, for you may not even have one, then surely you are much safer using the magnetic compass rose. For by doing this there is no chance of miscalculation. Sure use a GPS to find out where on earth you may be ( or a sextant if you were brought up in my time) but at he end of the day sticking to one formula is better than switching back aqnd forths. The magnetic rose has been printed there for a reason and that is so that you can use a "compass" to navigate your way.
As the author wrote if you are sailing along and using just a chart and a compass forget about your GPS showing true North, for you may not even have one, then surely you are much safer using the magnetic compass rose. For by doing this there is no chance of miscalculation. Sure use a GPS to find out where on earth you may be ( or a sextant if you were brought up in my time) but at he end of the day sticking to one formula is better than switching back aqnd forths. The magnetic rose has been printed there for a reason and that is so that you can use a "compass" to navigate your way.
Compass vs True
You have a point, and yes I am familiar with sextants. we must both be from the same generation. You certainly could use the magnetic rose for all of your navigation needs but when you go from one compass (steering) to another (hand-held for fixes) you better know your deveiations and how to apply them because both will be different. I much prefer thinking in "True" and adjusting all my equipment to true north. I am more comfortable with a known value that never changes, particularly on long voyages. At the end of the day it is the fixes you will be taking that will determine your real position and you will be adjusting your course to suit. Cheers.
You have a point, and yes I am familiar with sextants. we must both be from the same generation. You certainly could use the magnetic rose for all of your navigation needs but when you go from one compass (steering) to another (hand-held for fixes) you better know your deveiations and how to apply them because both will be different. I much prefer thinking in "True" and adjusting all my equipment to true north. I am more comfortable with a known value that never changes, particularly on long voyages. At the end of the day it is the fixes you will be taking that will determine your real position and you will be adjusting your course to suit. Cheers.
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