Maps?

Discussion in 'Free Thoughts' started by Pintsize, Jun 15, 2021.

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  1. Pintsize Registered Member

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    Are compass areas north (^), east (>), south (\/) and west (<)?

    is true north within the arctic (pole Earth turns round)?

    is the (ant-arctic) anti-arctic where south pole is?

    how is true north not magnetic north?

    who beleives north is way to scout?
     
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  3. sculptor Valued Senior Member

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    oh yeh
    and then we have assumed north
    if a property line is running east to west, then a perpendicular like to that line should be running north to south
    (which kinda depends on the surveyor)
     
    Last edited: Jun 15, 2021
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  5. DaveC426913 Valued Senior Member

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    Because we decided that true North points to the axis of Earth's rotation.

    This makes True (Geographic) North much more useful because:
    1] It's fixed - Magnetic North wanders all over, and
    2] It's applicable on any planet that rotates - whether or not it has a magnetic field.
     
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  7. exchemist Valued Senior Member

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    I do.
     
  8. Janus58 Valued Senior Member

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    The idea of a "true North" came before we had a magnetic compass. We noticed that the stars at night appeared to rotate around a particular fixed point in the sky. This made for a good reference upon which to base a common directional system. It wasn't until later that we learned to use magnets and found that a magnetized needle would point is nearly that same direction. Magnetic North and True North don't line up because the Earth's magnetic field is generated by convection currents of the Earth's fluid interior, and these are not entirely uniform. This causes the field to be offset from the axis of rotation a bit, and as noted by DaveC426913, to wander with time (even occasionally flipping, so the the Magnetic poles reverse).
     
  9. Pintsize Registered Member

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    what of the way water flows?
     
  10. Pintsize Registered Member

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    is this as goid as any for a direction to follow?

    does water flow to the lowest place?
     
  11. sculptor Valued Senior Member

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    For surveying in the USA, we line up with the "north star" to form the north south line of our grid.

    That creates a bit of an inaccuracy(<3/4 of a degree)
    which we live with
     
  12. DaveC426913 Valued Senior Member

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    It could create quite a bit of trouble if your 'North' changes hourly.

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  13. sculptor Valued Senior Member

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    ok
    how would a surveyor find the "True (Geographic) North"
    from 41 degrees north latitude?
     
  14. DaveC426913 Valued Senior Member

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    Surely there is already a way to do this. I mean, a half degree error in the boundary around a 100-acre plot would be .... 73 feet!

    If there isn't a more robust system already, I wonder why they couldn't apply a correction factor like they do for magnetic deviation on marine charts.
    Magnetic deviation only needs correcting every year or so, but the True North, you'd have to correct for time-of-day at moment of measurement.

    It would be pretty painless. A fixed (trig-based) plus or minus value per hour before/after noon to account for the precession of Polaris around the pole. Minimum at noon and midnight, max at 0600 and 1800.
     
  15. sculptor Valued Senior Member

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    ok
    I learned surveying back in the steel tape and bubble transit days
    and we would stay up past dark and find north via the north star
    then, the following day, start the survey from our "known north south" line.

    Much of this country was surveyed well over a century ago
    and those old boys left their markers for us(some of those markers were an X carved into a tree within a square of removed bark painted red) and most of our surveying relied on those old marks as starting points
    see above
    that is/was referred to as assumed north, or grid north

    For most purposes, that is the system we were/are stuck with.
    A few years ago, the army corps of engineers sent out some survey teams to find some of those old markers
    Using the latest tools(including gps) they relocated a few of those markers, some of which were off by as much as 3 feet(@1 meter)--------joking with one of the surveyors, I said: "I don't care what your GPS says, that ain't the Canadian river, and this ain't Oklahoma".
    Now: With more than one marker for the same grid location:
    The next guy will start out confused, and go from there.

    In the past 30 years 2 of my neighbors decided to put up fences, hiring surveyors with modern equipment to locate the boundaries
    So, I got my old equipment out and re-surveyed the property boundaries:
    The one on the north was ok(within a few inches) on the east end, but off by about 10 feet on the west end.
    The one on the south was ok on the west end, but off by about 8 feet on the east end.
    Both modern surveyors erred toward the south.
    The guy on the north moved his fence, the guy on the south didn't.

    Some surveyors strive for accuracy, some don't.

    ........................................
    reminds me of an old joke
    "which way is up?"
    (Bucky Fuller and I had a few laughs about that---away from or toward the center of gravity---which is in constant motion)
     
  16. exchemist Valued Senior Member

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    What do you think?
     
  17. sideshowbob Sorry, wrong number. Valued Senior Member

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    I actually knew somebody once who believed that water flows from the top of the map to the bottom.
     
  18. DaveC426913 Valued Senior Member

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    Yes. In a process called Continental Drip.

    (I have a one-frame cartoon somewhere in my gallery. Have you ever noticed how many land masses drip toward the South?)
     
  19. gmilam Valued Senior Member

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    I knew a guy once who claimed that all rivers turned towards the equator - because that is the center of the Earth.

    I pointed out the Nile to him and left him to figure it out for himself.
     
  20. Pintsize Registered Member

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    ***********o

    exchemist do i think the lowest place would be as good as any to begin mapping?
     
  21. exchemist Valued Senior Member

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    If you don't know what you think, there is not much point asking me.
     
  22. DaveC426913 Valued Senior Member

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    Where is this 'lowest place'?

    Sea level? The Continental Shelf? The Mariana Abyss?
     
  23. DaveC426913 Valued Senior Member

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    Don't forget Due North.
     
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