Computing heading

Jack Johnson fragment at nas.com
Sun Jan 4 08:41:19 UTC 2004


I was messing around with EToys and grabbed an arrow morph and a couple  
of ellipses and wanted to have the arrow morph automatically place  
itself between the two ellipses and point from one to the other.

The placement was easy, but I had trouble computing the heading.  I did  
come across a formula used for computing a bearing based on two map  
coordinates:

tc1=mod(atan2(sin(lon1-lon2)*cos(lat2),cos(lat1)*sin(lat2)- 
sin(lat1)*cos(lat2)*cos(lon1-lon2)),2*pi)

which would work just fine, but being relatively new to Squeak I'm at a  
loss for how to implement it, or how to even find out if/how Squeak  
implements the atan2 function.

Any pointers or suggestions?

-Jack




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