> My original question was based on the thought that I could create a hull from > the known points in each postal code and use those hulls as the sites in a > Voronoi.
This seems to make sense since you'll be effectively creating a convex polygon around each point for which you know the postal code. So if the original location of postal codes follows contiguous patterns then a simple algorithm much like coloring should yield groups of polygons with the same postal code. Whether this would look nice and eye-pleasing is another question ;) D.
