I'm not sure how to find out what version of GEOS I'm using
but I have deleted the shapely module and reinstalled it using the latest
version.
after that I also run a copy of your code
from shapely.geometry import MultiPoint
polya = MultiPoint([(-1.0, -2.0), (1.0, -2.0), (-1.0, 2.0),
(1.0,2.0)]).convex_hull
polyb = MultiPoint([(-1.0, -2.0), (1.0, -2.0), (-1.0, 2.0),
(1.0,2.0)]).convex_hull
buffa = polya.buffer(1.0)
buffb = polya.buffer(1.0)
print buffa.contains(polya)
print buffb.contains(polya)
print buffb.contains(polyb)
print buffa.contains(polyb)
print polya.equals(polyb)
which produces the following
False
False
False
False
True
I'm stuck
cheers
dan
> From: [email protected]
> To: [email protected]
> Date: Thu, 30 Jul 2009 14:11:11 +0200
> Subject: Re: [Community] buffer problem
>
> On Jul 28, 2009, at 8:55 PM, Daniel O'donohue wrote:
>
> > hi there
> >
> > I'm am trying to use the following algorthyim to test to see if two
> > geometries match
> >
> > Geometry A matches geometry B if
> > A is contained in buffer(B, d)
> > and B is contained in buffer(A, d)
> > and boundary(A) is contained in buffer(boundary(B), d)
> > and boundary(B) is contained in buffer(boundary(A), d)
> >
> >
> >
> > polya = MultiPoint([(-1.0, -2.0), (1.0, -2.0), (-1.0, 2.0), (1.0,
> > 2.0)]).convex_hull
> > polyb = MultiPoint([(-1.0, -2.0), (1.0, -2.0), (-1.0, 2.0), (1.0,
> > 2.0)]).convex_hull
> >
> > buffa = polya.buffer(1.0)
> > buffb = polya.buffer(1.0)
> >
> > polya_bound = polya.boundary
> > polyb_bound = polyb.boundary
> >
> >
> > print buffa.contains(polyb)
> > print buffb.contains(polya)
> > print buffa.contains(polyb_bound)
> > print buffb.contains(polya_bound)
> >
> >
> > I use a convex hull to ensure that the polygon created is only
> > considering the outside points
> > and my points are not ordered so this ensures that I valid polygon
> > is returned
> >
> > How ever the last four print statments return
> >
> > False
> > False
> > True
> > True
> >
> > both geometries are identical so why would the buffer of one not
> > contain the either one of the
> > original geometires??
> >
> > I am really studk here and would be greatfull for any help
> >
> > cheers
> >
> > dan
>
> Hi Dan,
>
> I can't reproduce this problem. Here's what I get, using Shapely
> 1.0.12 and GEOS 3.1.0:
>
> >>> from shapely.geometry import MultiPoint
> >>> polya = MultiPoint([(-1.0, -2.0), (1.0, -2.0), (-1.0, 2.0), (1.0,
> 2.0)]).convex_hull
> >>> polyb = MultiPoint([(-1.0, -2.0), (1.0, -2.0), (-1.0, 2.0), (1.0,
> 2.0)]).convex_hull
> >>> buffa = polya.buffer(1.0)
> >>> buffb = polya.buffer(1.0)
> >>> buffa.contains(polya)
> True
> >>> buffb.contains(polya)
> True
> >>> buffb.contains(polyb)
> True
> >>> buffa.contains(polyb)
> True
> >>> polya.equals(polyb)
> True
>
> What's your GEOS version?
>
> Sean
>
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