compass
- Thread starter DennisB
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Variation / Deviation Again...
Dennis I'm afraid, me heartie, that here we go again. Variation is 7 degree WEST (in 2001). Deviation is what your boat does to your compass and is unique to your vessel and compass. Now the terminology police can have at it. Stu
Dennis I'm afraid, me heartie, that here we go again. Variation is 7 degree WEST (in 2001). Deviation is what your boat does to your compass and is unique to your vessel and compass. Now the terminology police can have at it. Stu
Declination @ Bayfield, Wi.
Bayfield, Wi. @ 46.8N x 90.9W (May 14/04) Declination at 46.8N x 90.9 W = 1 ̊ 4' W - changing by 0 ̊ 5' W/year
Bayfield, Wi. @ 46.8N x 90.9W (May 14/04) Declination at 46.8N x 90.9 W = 1 ̊ 4' W - changing by 0 ̊ 5' W/year
declination calculator
Sorry, I didn't reference my source earlier. Compute your declination - From the U.S. NGDC: http://www.ngdc.noaa.gov/seg/geomag/jsp/Declination.jsp Geomagnetic Field Frequently Asked Questions: http://www.ngdc.noaa.gov/seg/geomag/faqgeom.shtml
Sorry, I didn't reference my source earlier. Compute your declination - From the U.S. NGDC: http://www.ngdc.noaa.gov/seg/geomag/jsp/Declination.jsp Geomagnetic Field Frequently Asked Questions: http://www.ngdc.noaa.gov/seg/geomag/faqgeom.shtml
Isn't It On Your Charts?
Around here it is 0 or close enought to it that it is not a real big issue so I do not remember for sure.
Around here it is 0 or close enought to it that it is not a real big issue so I do not remember for sure.
Variation/Declination
It seems like I tried to find this out once before, but at my age I have trouble remembering. I always used the term variation. Now the term declination is used. Isn't declination and variation the same thing?
It seems like I tried to find this out once before, but at my age I have trouble remembering. I always used the term variation. Now the term declination is used. Isn't declination and variation the same thing?
Variation/Deviation
Dan, Declination is generally not a compass term (except at very high latitudes - near the poles). It generally relates to the position of the sun over the earth relative to the equator. Variation is the magnetic north shift from true north FOR THE SPECIFIC LOCATION YOU ARE IN. You get the value from your latest chart in the compass rose on the chart for the date of the chart. It will also indicate how much the variation changes per year. Variation is for a specific geographic location and is for all boats. Deviation is the the magnetic north shift caused by the various metals (magnetic metals) on your boat. The value of deviation will be different for each compass direction that the boat is heading. So, you need a Deviation Table for your boat to give you the correct Deviation for your heading. Deviation is different for each boat. Hope this helps. Dick Carey S/V Puffin 1990 H-33.5
Dan, Declination is generally not a compass term (except at very high latitudes - near the poles). It generally relates to the position of the sun over the earth relative to the equator. Variation is the magnetic north shift from true north FOR THE SPECIFIC LOCATION YOU ARE IN. You get the value from your latest chart in the compass rose on the chart for the date of the chart. It will also indicate how much the variation changes per year. Variation is for a specific geographic location and is for all boats. Deviation is the the magnetic north shift caused by the various metals (magnetic metals) on your boat. The value of deviation will be different for each compass direction that the boat is heading. So, you need a Deviation Table for your boat to give you the correct Deviation for your heading. Deviation is different for each boat. Hope this helps. Dick Carey S/V Puffin 1990 H-33.5
More Declination
I went to Gord May's declination calcualtor. It looked like variation. It was the same as variation in my area. Still confused.
I went to Gord May's declination calcualtor. It looked like variation. It was the same as variation in my area. Still confused.
Believe Variation & Declination are the Same
I found a web site which has some information on compasses. It uses the term declination and does not mention variation. I assume that declination is a more modern or technically correct term for variation. The web site looks fairly interesting, but I did noy read it all.
I found a web site which has some information on compasses. It uses the term declination and does not mention variation. I assume that declination is a more modern or technically correct term for variation. The web site looks fairly interesting, but I did noy read it all.
Declination is Variation ...
The direction in which the compass needle points is referred to as magnetic north, and the angle between magnetic north and the true north direction is called magnetic DECLINATION. You will often hear the terms "variation", "magnetic variation", or "compass variation" used in place of magnetic declination, especially by mariners. Unfortunately, the annual change corrections (Secular variation) given on most charts & maps cannot be applied reliably if the maps are more than a few years old, since the secular variation also changes with time in an unpredictable manner. If accurate declination values are needed, and if recent editions of the charts are not available, up-to-date values for Canada may be obtained from the most recent geomagnetic reference field models produced by the Geological Survey of Canada. http://www.geolab.nrcan.gc.ca/geomag/cgrf_e.shtml For those interested in a little more (fascinating) background information, goto the Cruisers Forum (linked below), and click on "Instruments & Communications" the Where is North? Regards, Gord
The direction in which the compass needle points is referred to as magnetic north, and the angle between magnetic north and the true north direction is called magnetic DECLINATION. You will often hear the terms "variation", "magnetic variation", or "compass variation" used in place of magnetic declination, especially by mariners. Unfortunately, the annual change corrections (Secular variation) given on most charts & maps cannot be applied reliably if the maps are more than a few years old, since the secular variation also changes with time in an unpredictable manner. If accurate declination values are needed, and if recent editions of the charts are not available, up-to-date values for Canada may be obtained from the most recent geomagnetic reference field models produced by the Geological Survey of Canada. http://www.geolab.nrcan.gc.ca/geomag/cgrf_e.shtml For those interested in a little more (fascinating) background information, goto the Cruisers Forum (linked below), and click on "Instruments & Communications" the Where is North? Regards, Gord
Answer
The variation or declination is 1 degree 9 min west with a change of 0 degree 5 min west/year. Used Gords calculator and a zip code looker upper. It would be better if you used a local chart. Sometimes these types of tables do not take into account local variations in the overall field.
The variation or declination is 1 degree 9 min west with a change of 0 degree 5 min west/year. Used Gords calculator and a zip code looker upper. It would be better if you used a local chart. Sometimes these types of tables do not take into account local variations in the overall field.
calculator accuracy
Dan's partly right, use the compass rose on your chart. You don't really need to know declination/variation, if you don't have a chart. I got 1 degree 4 Min West (not 1 & 9) from the calculator, but the difference is insignificant in practice. I cannot see a minute on my compass, never mind steer to that accuracy. From my first post: Bayfield, Wi. @ 46.8N x 90.9W (May 14/04) Declination at 46.8N x 90.9 W = 1 ̊ 4' W - changing by 0 ̊ 5' W/year Gord
Dan's partly right, use the compass rose on your chart. You don't really need to know declination/variation, if you don't have a chart. I got 1 degree 4 Min West (not 1 & 9) from the calculator, but the difference is insignificant in practice. I cannot see a minute on my compass, never mind steer to that accuracy. From my first post: Bayfield, Wi. @ 46.8N x 90.9W (May 14/04) Declination at 46.8N x 90.9 W = 1 ̊ 4' W - changing by 0 ̊ 5' W/year Gord
If we call it
Declination, How do you remember compass uncorrecting? Timid Virgins Make Dull Companions At Weddings True Variation Mag. Deviation Compass Add West Any ideas?
Marc
Declination, How do you remember compass uncorrecting? Timid Virgins Make Dull Companions At Weddings True Variation Mag. Deviation Compass Add West Any ideas?
Marc- Status