[Gdal-dev] remove colinear points from polygon
Christian.Martel at drdc-rddc.gc.ca
Tue Mar 6 08:20:17 EST 2007
I know many solutions to remove colinear point but I want to use the
available tools in OGR and get a quick and simple function. So here is
what I did in python. Don't know about performance againt another
"remove colinear points from polygon boundary"
gUnion = polygon #geometry resulting of
Union of several polygons
gHull = gUnion.ConvexHull() #create a geometry without
gOver = gHull.Difference(gUnion) #exceding part of the convexHull
gFinal = gHull.Difference(gOver) #get back the original geometry
without colinear point
> -----Original Message-----
> From: Mateusz Loskot [mailto:mateusz at loskot.net]
> Sent: 6 mars 2007 03:14
> To: Martel, Christian
> Cc: gdal-dev at lists.maptools.org
> Subject: Re: [Gdal-dev] remove colinear points from polygon
> Martel, Christian wrote:
> > Hi,
> > After merging several polygons with union, I get a big polygon with
> > many colinear points. Example : with line (0 0,1 0,2 0), 1 0 is
> > colinear with the others. How can I remove these middle colinear
> > points on the polygon border ?
> The most universal method is to use use Douglas-Peucker
> algorithm for polyline simplification (implemented in GEOS).
> Another possible solution is to calculate and compare slopes
> between adjacent points.
> There is also an option based on distance formula and
> ordering points of line, but this one is usually slower than
> these two above.
> Mateusz Loskot
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