[prev in list] [next in list] [prev in thread] [next in thread] 

List:       postgis-users
Subject:    Re: [postgis-users] Topology precision
From:       Marc-Antoine_Nüssli <nuessli.ma () gmail ! com>
Date:       2018-07-10 9:22:27
Message-ID: CAO6t8Z9Jr9Ek3LbjPCB2ALgX4U5eJNYGmATBsQD1hYbO9h6QSA () mail ! gmail ! com
[Download RAW message or body]

[Attachment #2 (multipart/alternative)]


Thank you for your answer!
This is much clearer now. So, I will continue to live with floating
precision operations for the moment.

Best regards,
man

Le ven. 6 juil. 2018 =C3=A0 22:34, Sandro Santilli <strk@kbt.io> a =C3=A9cr=
it :

> On Fri, Jul 06, 2018 at 11:25:16AM +0200, Marc-Antoine N=C3=BCssli wrote:
> > Hi there,
> >
> > First, I want to say a big thanks to Sandro Santilli and all people who
> > work on the topology features. It looks like it becomes now mature enou=
gh
> > to be used for production applications and this is really great to mana=
ge
> > geo-data much more consistently than with simple geometries (especially
> > when you deal a lot with territorial partitions like in my case)
>
> Thanks for the feedback!
>
> > I have a question regarding the precision value that we have to provide
> > when creating a topology. I am not sure to understand its purpose.
> > Somehow, I would have expected that it would be used when computing new
> > nodes positions, for example resulting from an intersection, but from m=
y
> > tests it seems it is not the case (see my example below)
> > Do you have some links or other infos that would describe how & when th=
is
> > global topology precision parameter is used?
>
> Using it for nodes position is planned. Doing so will need introduction
> of the concept of fixed-precision operations which are still unavailable
> in PostGIS. Such operations would first enforce snapping of input
> geometries to a fixed-precision grid and then ask GEOS to perform the
> operation using that grid.
>
> Right now PostGIS Topology only uses the "precision" value to snap
> incoming lines and vertices to existing nodes and vertices when using
> toTopoGeom or the underlying TopoGeo_addPoint, TopoGeo_addLinestring
> and TopoGeo_addPolygon and not overriding the global value.
>
> --strk;
>

[Attachment #5 (text/html)]

<div dir="ltr">Thank you for your answer!<div>This is much clearer now. So, I will \
continue to live with floating precision operations for the \
moment.<br></div><div><br></div><div>Best regards,</div><div>man</div></div><br><div \
class="gmail_quote"><div dir="ltr">Le  ven. 6 juil. 2018 Ã   22:34, Sandro Santilli \
&lt;<a href="mailto:strk@kbt.io">strk@kbt.io</a>&gt; a écrit  :<br></div><blockquote \
class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc \
solid;padding-left:1ex">On Fri, Jul 06, 2018 at 11:25:16AM +0200, Marc-Antoine \
Nüssli wrote:<br> &gt; Hi there,<br>
&gt; <br>
&gt; First, I want to say a big thanks to Sandro Santilli and all people who<br>
&gt; work on the topology features. It looks like it becomes now mature enough<br>
&gt; to be used for production applications and this is really great to manage<br>
&gt; geo-data much more consistently than with simple geometries (especially<br>
&gt; when you deal a lot with territorial partitions like in my case)<br>
<br>
Thanks for the feedback!<br>
<br>
&gt; I have a question regarding the precision value that we have to provide<br>
&gt; when creating a topology. I am not sure to understand its purpose.<br>
&gt; Somehow, I would have expected that it would be used when computing new<br>
&gt; nodes positions, for example resulting from an intersection, but from my<br>
&gt; tests it seems it is not the case (see my example below)<br>
&gt; Do you have some links or other infos that would describe how &amp; when \
this<br> &gt; global topology precision parameter is used?<br>
<br>
Using it for nodes position is planned. Doing so will need introduction<br>
of the concept of fixed-precision operations which are still unavailable<br>
in PostGIS. Such operations would first enforce snapping of input<br>
geometries to a fixed-precision grid and then ask GEOS to perform the<br>
operation using that grid.<br>
<br>
Right now PostGIS Topology only uses the &quot;precision&quot; value to snap<br>
incoming lines and vertices to existing nodes and vertices when using<br>
toTopoGeom or the underlying TopoGeo_addPoint, TopoGeo_addLinestring<br>
and TopoGeo_addPolygon and not overriding the global value.<br>
<br>
--strk;<br>
</blockquote></div>


[Attachment #6 (text/plain)]

_______________________________________________
postgis-users mailing list
postgis-users@lists.osgeo.org
https://lists.osgeo.org/mailman/listinfo/postgis-users

[prev in list] [next in list] [prev in thread] [next in thread]