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Compasses point to true north

Discussion in 'Bushcraft Chatter' started by Woody girl, Aug 30, 2019.

  1. Van-Wild

    Van-Wild Nomad

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    Absolutely. Always have a quick peek behind you every now and then! You never know......

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  2. Janne

    Janne M.A.B (Mad About Bushcraft)

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    even if you have just passed an area, walking it in the opposite direction, the same stretch, you walk In virgin, unseen territory.
    Looking back helps a bit.

    For my navigation, I have relied hugely more on a map than a compass, as in Scandinavia there are areas with a higher iron content in the ground that can mess with the compass.

    Even large boulders, remnants from Ice Age, transported by the ice from iron ore rich deposits, can momentarily affect it.
    I do not know if you have such areas in UK?
     
  3. Tengu

    Tengu Full Member

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    I navigate by landmarks.

    and the sun.

    Not sure about these newfangled magnetic things...but there was that bit in the Inventio Fortunatia...
     
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  4. Paul_B

    Paul_B Bushcrafter (boy, I've got a lot to say!)

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    Has anyone read if grid north is changing?:)

    There is a sketch of the three north's and their relative difference on every GB os map. It also tells you the degrees magnetic north changes per year. Look at map publishing date and adjust accordingly.

    All probably well known by people on here but just in case no harm in preaching to the converted if it gets a new convert or two for basic map knowledge.

    The question is whether GB OS has adjusted for a speeding up of the drift?l

    Just a point about laying out your compass collection on the table. The needles can interact pulling them out of alignment with the magnetic field. Pointing out you're obvious!

    Navigation is really about a collection of skills and techniques. Sometimes it is down to other senses than the traditional 5 senses. Above all it's about common sense. That's a rare thing at times, certainly in the lakes near me. If you visit an area once a year or have only been there once or twice you really can't leave your map behind. Trust me you cannot do a route that would take a good fell runner a couple if hours to do when it's winter and you've only just got enough time to get off here hills in the remaining daylight. Oh you don't have torches of any kind? So you have no map only a set if written directions for a selection if walking routes? Shall I call MRT before I drop out of mast range or from the pub at the bottom of the hill?

    I really like navigation. It's a lifelong journey of discovery. You can always learn more. There's a good book called natural navigation iirc, it's about using nature not maps and compass and gps for navigation.
     
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  5. Winnet

    Winnet Forager

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    Grid north is grid north and won't change, it is the same with True north. That is ignoring convergence which is the difference between grid north and true north which varies depending on where you are.

    Magnetic north is the only one that moves around and needs adjusting for.

    G



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  6. Wayland

    Wayland Hárbarðr

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    Yep, wot ee sed...
     
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  7. Janne

    Janne M.A.B (Mad About Bushcraft)

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    Yep. True North and South are the exit points for the imaginary axis.
    If those change I imagine we are in a very deep pile of natural fertilizer!
     
  8. Tengu

    Tengu Full Member

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    Its happened many times in the past. Im sure we will get used to it
     
  9. Paul_B

    Paul_B Bushcrafter (boy, I've got a lot to say!)

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    Isn't it the magnetic poles that changed not true north south? Doesn't that oscillate towards and away from the sun as the earth goes round the sun but can't really flip?
     
  10. Janne

    Janne M.A.B (Mad About Bushcraft)

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    Magnetic poles are wandering, yes.
    Has been flipping since Eve cheated on Adam with a snake.
    The earth axis is tilted and oscillates.

    The tilt angle has been varying a few degrees, but not much. I do not think the Earth has ever done a flip in that direction.
    I do not know if anybody knows the movement of the Earth in its very early history?
     
  11. Paul_B

    Paul_B Bushcrafter (boy, I've got a lot to say!)

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    IIRC magnetic direction is measurable in rock, igneous rock AIUI. The true north/ south axis is something that can be observed not measured. I guess we'll never know what happened prior to humans making and recording the observations of this.
     
  12. Winnet

    Winnet Forager

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    The north south axis through the poles was defined by surveyors many years ago and is mainly used to give a set reference frame. There were lots of arguments as to where 0⁰ line of longitude should run, the French wanted it through Paris but the Brits won with it going through Greenwich.

    G.

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  13. Robson Valley

    Robson Valley Full Member

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    The sea floor spreading along the mid-Atlantic ridge has given us millions of years of magnetic field data, trapped in the rock as it cooled.
    It's possible that some wobbles might be recorded as well?

    Take a good look = Polaris will NOT be the pole star in another 10,000 - 12,000 years.
    There's even a record of the effect of earth's spin wobble in the construction of Stone Henge.
     
  14. Janne

    Janne M.A.B (Mad About Bushcraft)

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    I think Woody Girl tasted her Rowanberry Vodka so she got into some wobbling......

    :)
     
  15. Woody girl

    Woody girl Full Member

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    Grid north and the North Pole are not changing. It's just magnetic north which now aligns with the Greenwich meridian for the first time since records began.
     
  16. Janne

    Janne M.A.B (Mad About Bushcraft)

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    Grid north is the North Pole.
    Correct?
    The Americans think Santa lives there.......
     
  17. bearbait

    bearbait Full Member

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    Agreed.

    I like to work on the principle that Navigation is the Art Of Knowing That You Are Not Where You Think You Are.
     
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  18. Woody girl

    Woody girl Full Member

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    I always remember being told the art of navigation is getting from a to b without hitting points c d and e before you get to point b.
     
  19. Robson Valley

    Robson Valley Full Member

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    There are logging trails abandoned 50+ years ago throughout the mountains of my district.
    Stick to those trails, it's hard to get "turned around." Easy walking, level camp sites, as good as it gets.
    BUT
    Any kind of a sudden, heavy mountain snowfall and the compass is crucial.
    All landmarks disappear. Visibility might be 50-75 yards. Everything looks the same.
    Could be an inch, might be 2 feet. Best to get out or down or both.
     
  20. Winnet

    Winnet Forager

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    No, that is True north.

    Grid north depends on the mapping sheroid/datsun being used and where the central meridian is for it.

    Look up diagrams for Universal Transverse Mercator (UTM) and you should be able to see the effect.

    G

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