Sgt_Strider Posted December 9, 2014 Share Posted December 9, 2014 If I have a reading that is based on the magnetic north, can it be easily converted to true north? The problem is that the magnetic north pole changes over time. I'm not aware of any method and I'm hoping someone here can help. Quote Link to comment
+Timpat Posted December 9, 2014 Share Posted December 9, 2014 If this is in regard to a cache with projecting a point, simply change your settings to Mag north, enter the given data, then switch your settings back to True north. As a side note, I believe Garmin issues updated mag declination data with firmware updates to keep up with changes. Quote Link to comment
Sgt_Strider Posted December 9, 2014 Author Share Posted December 9, 2014 If this is in regard to a cache with projecting a point, simply change your settings to Mag north, enter the given data, then switch your settings back to True north. As a side note, I believe Garmin issues updated mag declination data with firmware updates to keep up with changes. No, this have nothing to do with a cache. Quote Link to comment
+Bear and Ragged Posted December 9, 2014 Share Posted December 9, 2014 (edited) If this is in regard to a cache with projecting a point, simply change your settings to Mag north, enter the given data, then switch your settings back to True north. As a side note, I believe Garmin issues updated mag declination data with firmware updates to keep up with changes. No, this have nothing to do with a cache. What are you using? Phone/GPS/on a computer? Map and compass? (The previous reply is correct, if you are using a GPS and have a set of coordinates...) Would also help, if you gave some indication of your location, as things vary according to location! Try Wiki for help and a few links. http://en.wikipedia.org/wiki/Magnetic_declination Edited December 9, 2014 by Bear and Ragged Quote Link to comment
+Timpat Posted December 9, 2014 Share Posted December 9, 2014 Well then, if you could, be more specific about what you are hoping for? In my survey work I use NGDC Geomagnetic Calc site. For example an old property deed may say bearings are based on "as the magnetic needle pointed in 1856". I can use the linked site to determine what the declination was for a particular Lat/Lon location in the past and correct it based on current declination. Quote Link to comment
DavisonDave Posted December 9, 2014 Share Posted December 9, 2014 If I have a reading that is based on the magnetic north, can it be easily converted to true north? The problem is that the magnetic north pole changes over time. I'm not aware of any method and I'm hoping someone here can help. Go to http://geomag.nrcan.gc.ca/calc/mdcal-eng.php you can enter the date and lat/long you would like the conversion for. It will give you a magnetic declination to add or subtract to switch from magnetic north to from true north. If the number is west subtract it to go from mag to true north, if its east add it to go from mag to true north. Quote Link to comment
Sgt_Strider Posted December 9, 2014 Author Share Posted December 9, 2014 Well then, if you could, be more specific about what you are hoping for? In my survey work I use NGDC Geomagnetic Calc site. For example an old property deed may say bearings are based on "as the magnetic needle pointed in 1856". I can use the linked site to determine what the declination was for a particular Lat/Lon location in the past and correct it based on current declination. Awesome site! In terms of accuracy, the website said results are typically accurate to 30 min. of arc. What does that mean in terms of accuracy? Is the accuracy going to be true for any point in the globe? I know it's from the NOAA and I expect good accuracy for the US and pretty much North America, but I don't know about elsewhere in the world. Also, what is the difference between IGRF 11 and WMM 2010? Which is the standard most used? Quote Link to comment
+Lil Devil Posted December 9, 2014 Share Posted December 9, 2014 Is the accuracy going to be true for any point in the globe? I know it's from the NOAA and I expect good accuracy for the US and pretty much North America, but I don't know about elsewhere in the world. Think about it. They didn't go and survey the US every year. But they do know reasonably well where on the globe the magnetic north pole was. From that it's simple mathematics to compute the declination for any point on the globe. So I would expect the accuracy to be the same world-wide, which logically means very good accuracy at lower declination numbers and less accuracy (up to 30 min, or 1/2 degree) for higher declinations. Quote Link to comment
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