[postgis-users] line simplication

strk strk at freek.keybit.net
Wed Jan 8 09:54:41 PST 2003

I think postgis should do this. I'd like helping with it.

For the sorrouding environment problem:

"The use of spatial context in linear feature simplification"


andy wrote:
> Douglas Peucker is a useful algorithm, but you need to be careful with
> it in a mapping setting. The algorithm basically removes points from a
> linestring that don't change it too much.
> The problem is that the algorithm has no knowledge of the surrounding
> environment. Intersections are a good example. If you have a normal
> intersection of two street segments, moving the point of intersection a
> little doesn't harm the map much.
> However, D-P may take T-intersection and transform it either into two
> disconnected lines or two lines that cross each other. Neither of these
> looks correct visually and may cause other problems in interpretation.
> Also, D-P operates in a cartesian space and applying it to raw lat/lon
> data probably wouldn't work right.
> On Mon, 2003-01-06 at 16:47, Paul Ramsey wrote:
> > Precisely correct (I think). The best way to the desired result should 
> > be to implement a Douglas simplification function, and then create a 
> > view which (a) uses attributes to reduce to just the features of 
> > interest (interstates, etc) and (b) uses the simplify() function to 
> > remove unnecessary vertices from the features.
> > 
> > P.
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