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For a long time, I've been wondering for myself: if I know for sure that a certain house has this wall facing West, and I'm standing facing the wall in front of me, and I have nothing else to go by, does that automatically mean that North must be to my left, and thus South to my right, with the East compass direction on the other side (in front)?

Do I only need to know one direction to determine all the others, or does it require knowing at least two ones which aren't opposites of each other?

And does this differ depending on which direction I know? For example, if I know for a fact which direction is South, does that mean that I know which side is West and East?

I hope that I've made myself clear.

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  • 1
    Yes, that is sufficient.
    – Jon Custer
    Oct 22 '20 at 18:50
  • 1
    Sufficient so long as you're in gravity, not free fall. Oct 25 '20 at 2:25
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Compass directions are, generally, always equally spaced around the circle. The cardinal directions -- North, East, South, West -- are always 90 degrees apart. If you know any one direction you should always be able to determine any other direction.

That said, there are some caveats. Magnetic compass directions are actually under the influence of the local magnetic force field and magnetic N-S lines can be very different from geographic (or true) N-S lines, so be careful regarding which (magnetic or true) directions you are using. Also, the closer you are to the poles, the less meaning compass directions have. (Imagine standing at the North pole, everywhere you face will be South! and where is East or West?)

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  • Not many people will ever stand on the North pole. And for most the variations of the magnetic and map north will not be that confusing, (but mentioning them in this answer is confusing the matter.)
    – Willeke
    Oct 25 '20 at 18:47
  • @Willeke: I gave some extra things to consider, to help improve knowledge and understanding.
    – Martin F
    Oct 26 '20 at 20:33
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I agree with the other answer that one direction is enough to determine the others. As for actually doing it, it's very easy but can be confusing if your mind is overwhelmed by other things (e.g. if you are about to win or lose a race, or are very drunk).

I use the following rules:

  • If you are facing north, east is to your right, and west to your left
  • If you are facing in another direction, physically turning to face north is silly but may help if you feel really drunk
  • If you have good visual memory, recall a map of the area you are in - this should make you instantly "feel" which direction is which

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