point-to-polygon

[nps!peter at cerl.cecer.army.mil]

 | To transform our geometric data to GRASS I am looking for an algorithm to
 | find a point for an area polygon which is definitely inside the polygon.
 | It's a kind of point-in-polygon question, but I have the polygon not the
 | point. 

I have an algorithm, coded in Fortran, that finds such a point.  First it
calculates a "centroid" from the mean of the x and y values.  If that point
is found to be outside the polygon, it locates the closest line segment to
the "centroid".  From there, a sequence of points are tested along the 
perpendicular to that line segment, until an inside point is found.  If you
are interested, I will be happy to e-mail you the source code.

-------------------------------------------------------
	Peter Strong
	National Park Service
	@cerl.cecer.army.mil:nps\!peter