declination.

Discussion in 'Adventure, Hiking, Backpacking and Travel' started by charlie, Dec 9, 2017.

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  1. charlie

    charlie Member

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    i live in west lafayette, indiana. how do i go about figuring out what the declination is for my area?
     
  2. SEMO

    SEMO Member

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  3. charlie

    charlie Member

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  4. SEMO

    SEMO Member

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  5. junglebum

    junglebum Member

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    If it has a magnetic declination adjustment then you will set the “ inner crystal” so that the dog house faces 356... if it doesn’t then you will have to do the math
     
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  6. Jim

    Jim Member

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    A picture is always helpful in imagining how the magnetic field curves with respect to your location

    [​IMG]


    For your location the compass needle is pointing 4 degrees to the West (left) instead of straight up at true North. Your compass' adjustment allows the outer azimuth ring that is labeled "N" to be aligned with true North while the needle itself is pointed 4 degrees to the West.
     
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  7. Bushman5

    Bushman5 Member

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    20171210_065322.jpg
     
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  8. Jim

    Jim Member

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    Are you actually in the Vancouver area? Vancouver's declination should be 16 degrees to the east. Putting a compass anywhere near a computer is liable to influence the reading.

    Latitude: 49° 22' 11.9" N
    Longitude: 123° 6' 30.2" W
    Magnetic declination: +16° 18'
    Declination is POSITIVE (EAST)
    Inclination: 70° 17'
    Magnetic field strength: 54228.0 nT
     
  9. Jeff Randall

    Jeff Randall ESEE Knives / Randall's Adventure & Training Staff Member

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    west is best, east is least. So if you are going from map to the real world you would add declination. In other words, if you measured the azimuth on the map as 10 degrees then you would walk 14 degrees if you have 4 degrees west declination. If you are going from real world back to map then you would subtract. So, if you were sighting a mountain peak and it was 10 degrees on your compass and you wanted to translate that back to the map then it would be 6 degrees on the map for west declination. If you are east declination then everything is reverse of what I just said.

    With all that said, declination can be grid or magnetic and it all depends on what you are using for your reference when measuring angles on the map. If you are using grid lines to measure your angle (azimuth) then use the grid declination for the area. If you are using Longitude lines (true north lines) then use the magnetic declination.

    Confusing until you do it a lot and understand it. Best thing for those who are new to this is buy a compass that you can set declination on then set it and forget it. You just have to make sure what the declination is for the area you are working and also make sure if you are using grid or magnetic on your map.
     
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  10. Bushman5

    Bushman5 Member

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    yea in van.....and yes ours is 16 east. I was just posting a photo of what Charlies dec would look like. I had it at 4 deg but the camera affected that when i snapped it. lol
     
  11. charlie

    charlie Member

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    website says at top of page-9.89. where you get -4 west?
     
  12. Jeff Randall

    Jeff Randall ESEE Knives / Randall's Adventure & Training Staff Member

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  13. Jeff Randall

    Jeff Randall ESEE Knives / Randall's Adventure & Training Staff Member

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    Semo's map he posted is in Pennsylvania, but then again he thinks the US borders Austria.
     
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  14. Jeff Randall

    Jeff Randall ESEE Knives / Randall's Adventure & Training Staff Member

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    This is an old map. The Agonic line is now basically cuts through Memphis on the TN / AR border. Declination where I live is right at 4 degrees West now.
     
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  15. Jeff Randall

    Jeff Randall ESEE Knives / Randall's Adventure & Training Staff Member

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    Here's the current map from NOAA

    Yellow line is the Agonic line (0 degrees declination). Every blue line east of that is one degree west declination. Every red line west of the yellow line is 1 degree East declination.

    Screen Shot 2017-12-16 at 1.53.21 PM.png
     
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  16. Jeff Randall

    Jeff Randall ESEE Knives / Randall's Adventure & Training Staff Member

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    And just for fun, here's the declination map when we were fighting the British in 1776. Mike Perrin remembers those days.

    Screen Shot 2017-12-16 at 2.03.16 PM.png
     
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  17. charlie

    charlie Member

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    totally cool. thanks for the info.
     
  18. McKROB

    McKROB Member

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    Touched on above, but don’t forget that declination changes each year, topo sheets will usually state the annual rate of change on the map, and you need to calculate the change from the year the map was published to present day by adding or subtracting it to the declination stated on the map.

    If in high latitudes the magnetic declination can even vary significantly from the centre of the map to the edges of the map, and this must also be taken into account when on long traverses.

    There is a little trick to get the current declination out of your Garmin, this is what I always use to set my compass. Make sure the Garmin is on and position up to date (you have satellites). From the Setup menu, choose Heading. Under North Reference, the default setting is True (ie. true north), there are three other menu options here, Magnetic, Grid, and User. Choose User and you will see that the value displayed is 000E. Exit, then go back and change this to Magnetic and hit enter. Return once again and select User, now the field will have changed from 000E and will be populated with your current declination. Use this value to set your compass. Don’t forget to now change this back to True.
     
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