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I got angles in mathematical sense. This means 0° is east and the rotation is anti-clockwise.

I need to convert them to 0° is north plus rotation clockwise.

The first one is an easy offset but how can I build up an algorythm taking into account to rotation direction?

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I have thought about getting X/Y in a circle with radius=1. But I dont know which angle functions will then return in the correct new system when going back from X/Y to the angle. –  ZoolWay Feb 24 '12 at 18:31
    
If $\theta$ is the angle anticlockwise from east in degrees, then the angle clockwise from north is $90^\circ - \theta$. –  Rahul Jun 2 '12 at 0:37
    
+1 fuer "algorythm" –  Sibbs Gambling Oct 1 '13 at 3:43

1 Answer 1

up vote 0 down vote accepted

Okay, maybe asking it helped me ;)

How does this look:

x = cos(mathAngle) y = sin(mathAngle)

otherAngle = arctan(x / y)

The test values look nice to me. Switching x and y for arctan changes the rotation direction.

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