R: Thread on navigation / compasses.

From: Simon D. Hibbs (S.Hibbs@fcrd.gov.uk)
Date: Wed 07 May 1997 - 11:54:29 EEST


I suppose I should own up some responsibility for this thread, as it
orriginated in a conversation with Philip ages ago (a year or more).

All that two compases, each pointing in different directions, tells you is
the angle between the directions they are pointing in. That's it. They
give no other information.

The angle between two refference points is not enough to give you a unique
location.

On land, or at sea looking at land, you can often narrow down your
location sufficiently using other visual clues. Also, in Glorantha, you
have other information to help. For example, at dawn and dusk you also
know the direction of the sunrise and sunset. etc.

Thomas Gottschall :

>Take a piece of paper and mark to points A and B. This are the points
>your two compasses are pointing at. Choose a point X. This is the point

Whoa there. The point X is what you are trying to find. How can you start
out looking for it by arbitrarily sticking it on the map at the begining
of the excercise. That's ludicrous.

>where you stand. Now decide to what directions both compasses point.
>Draw a line through point A with the direction your compass showed you,
>do the same with B. The meeting point is X of course. This is how you
>can say where you are if you have a map. Without a map you can't do it.

As I said earlier. All you acualy have is the angle between the lines to
point A and point B.

Anyway, Phil and I sorted this out ages ago. Check his diagram, I imagine
it's similar to the ones we used to convince ourselves.

Simon

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