fork <forkandwait <at> gmail.com> writes: > I found it CRAZY how many different types of DE-9IM's could be returned, even > with just polygons and very well aligned boundaries (credit to the US Census > Bureau's geography division). Only a few of the matrices in my data were > actually described in the few docs I could find.
For a flavor, look at Table 3 here: http://www.cise.ufl.edu/~mschneid/Research/papers/BS01ER.pdf Note that these matrices are boolean for the intersection, and there are 32 of them. One can tweak them so that the max dimension on the boundaries is either 0 (a point) or 1 (a line) and create more matrices using the full definition of DE-91M; see #33. I am mostly just entertaining myself with mathematical patterns, but I think the topological matrices might be useful in trying to figure out how to simplify slivers and weird things. I also think one's intuition about "within" might not stand up to closer scrutiny via mathematical formalisms like this. The only way I could figure out my blocks-in-cities problem was to abandon st_within() etc and go for a list of specific DE-9IM's based on the data. If I feel bored/ ambitious I will try to create a useful atlas. I don't think one exists... _______________________________________________ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
