[postgis-devel] Re: Rounding off coordinates (from Postgis-users)

strk strk at keybit.net
Thu Jul 1 08:41:22 PDT 2004


On Thu, Jul 01, 2004 at 05:18:11PM +0200, Markus Schaber wrote:
> Hi, Strk,
> 
> On Wed, 30 Jun 2004 02:08:05 +0200
> strk <strk at keybit.net> wrote:
> 
> > Gino, about removing points:
> > 	- You'll never introduce self-intersections
> 
> One can introduce self-intersections by removing or rounding points.
> 
> Example for the first:
> 
>     |
>     | 
>     *-----* 
> --------* |
>         | |
>         | |
>         | |
>         | |
>         | *---
> 
> Now, you remove the point of the outer corner because it is too near to
> the two next points:
> 
>     |
>     | 
>     * 
> -----X--*
>       \ |
>        \|
>         X 
>         |\
>         | *---
> 
> It's no exact graphics, but I think it should be enough to get the
> idea...
> 
> Markus

What I implemented did not remove points with 'too-near' checks.
I tough you were doing something similar. RoundingOff primary
purpose should be Rounding, not points reduction.
What I did is removing points which made really no-sense keeping,
which is consecutive points having the same coordinates and 
multiple back-and-forth between two points.

--strk;

> 
> -- 
> markus schaber | dipl. informatiker
> logi-track ag | rennweg 14-16 | ch 8001 z├╝rich
> phone +41-43-888 62 52 | fax +41-43-888 62 53
> mailto:schabios at logi-track.com | www.logi-track.com



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