I have an identical Python cgi-bin script running on two servers - one a
Windows 2003 server and the other my desktop (Windows 7 64-bit). The script
uses Shapely prepared polygon geometries to test whether a large number of
points fall within given polygons. I get different results from both servers.
Both are running Python 2.7.
Here are some code snippets:
from shapely.geometry import Point, Polygon
from shapely.wkt import loads
from shapely.prepared import prep
#read in file of livestock areas in WKT format and create list of Polygons
allf = open("poly_geom.txt","r")
lines = allf.readlines()
lsrs = []
polys = []
polysdict = {}
for line in lines:
lsr,geom = line.strip().split("|")
lsrs.append(lsr)
poly = loads(geom)
prpoly = prep(poly)
polysdict[lsr] = prpoly
polys.append(prpoly)
#Later, using a list of points (allpts) I do:
polyidx = 0
for prpoly in polys:
a = [pt for pt in allpts if prpoly.contains(pt)]
lsr = lsrs[polyidx]
alldict[lsr] = len(a)
print lsr + ":" + str(len(a))
polyidx = polyidx + 1
On the Windows 2003 server I get almost double the numbers of points falling
within each polygon. I have checked using a GIS and spatialite, and my desktop
(Windows 7) returns the correct results. On the server, if I use unprepared
polygon geoemetries, I get the correct answer. ie. I replace the first section
of code with:
for line in lines:
lsr,geom = line.strip().split("|")
lsrs.append(lsr)
poly = loads(geom)
#prpoly = prep(poly)
polysdict[lsr] = poly
polys.append(poly)
Is there a bug in the prepared code or does Shapely rely on other installed
components (Geos) etc. such that I might have an older dll somewhere?
Many thanks,
Robert
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