Re: CALCULATION OF AREA ON A SPHERE

[Craig Markwardt <craigmnet(at)cow.physics.wisc.edu>]

Med Bennett <mbennett@indra.com> writes:

> This is an interesting problem and I was hoping that someone would have
> provided a slick answer by now.  I started searching the Web and came up
> with the following.  It seems as though you could triangulate your points
> and then use the theorem presented below:
> [ ... deleted ... ]

This was discussed a little bit in August 1999 (see "area enclosed by
a polygon on a sphere" on www.deja.com).  The tricky part of course is
computing the correct angles.  Struan Gray wondered if there was a
utility routine in the idlastro library which could help.

Try GCIRC of idlastro, but also these two from the "JHU/APL/S1R usr
Library".

SPHGC Find intersections of two great circles on sphere. 
SPHIC Compute intersection points of two circles on a unit sphere. 

I found these here:
http://www.astro.washington.edu/deutsch/idl/

Craig

P.S.  A little research is all it takes!

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Craig B. Markwardt, Ph.D.         EMAIL:    craigmnet@cow.physics.wisc.edu
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