[postgis-users] Doubt about toTopoGeom tolerance

[Alexandre Neto]

Hi,

I am not sure I understood your affirmation. wanting to snap to the nearest
edge, its the same as using a very large tolerance.

Alexandre Neto

On Wed, Jul 1, 2020 at 3:47 PM Alexandre Silva <
amsilva at infoportugal.impresa.pt> wrote:

> Hi,
>
> Thank you for your response.
>
> I tried the solution you provided and the result was the same, however
> after increasing the tolerance the geometry did indeed snap to a nearby
> node.
> I thought that the snap was to the closest point on a nearby edge but it
> seems that it only snaps to nodes within the tolerance. What's the best way
> to snap a geometry to the closest point on a nearby edge? I cannot increase
> the tolerance as it would be error prone (to make the snap on one specific
> geometry I had to increase it from 0.1m to 0.5m).
>
> Thank you for your assistance,
> Alexandre Silva
>
>
>
>
>
>
>
> ------------------------------
> *De:* postgis-users <postgis-users-bounces at lists.osgeo.org> em nome de
> Alexandre Neto <senhor.neto at gmail.com>
> *Enviado:* 29 de junho de 2020 23:49
> *Para:* PostGIS Users Discussion <postgis-users at lists.osgeo.org>
> *Assunto:* Re: [postgis-users] Doubt about toTopoGeom tolerance
>
> Hi,
>
> I have looked into the documentation, and it seems that there are two form
> of using toTopoGeom:
> 1. One to add new topogeometry an existing topology layer, and another to
> change an element. This is what you seem to be using.
> 2. The second form, with less arguments, is used ADD changes to existing
> topoGeometries. But, it says you may want to use clearTopoGeom(topo) to
> create a totally new shape.
>
> My gut feeling is that since you already have the topogeometry in the
> topology, when you try to add it again, it will snap to the old geometry
> any way.
> My first try would be something like:
>
> UPDATE lines_table
> SET topo = topology.toTopoGeom(geom, clearTopoGeom(topo), 0.1)
> WHERE id = 1263;
>
> http://postgis.net/docs/manual-dev/toTopoGeom.html
> <https://eur01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fpostgis.net%2Fdocs%2Fmanual-dev%2FtoTopoGeom.html&data=02%7C01%7Camsilva%40infoportugal.impresa.pt%7C993cd4fd7266463c411908d81c7eb1b3%7Cd227b2e71c404f63b5132f3665c334e6%7C0%7C1%7C637290677762157357&sdata=V0GsN0KHhm5zLvM6S4aQRg%2F%2FFCP6jsNuWeX08aoVAjc%3D&reserved=0>
>
> Good luck,
>
> Alexandre Neto
>
> On Mon, Jun 29, 2020 at 5:53 PM Alexandre Silva <
> amsilva at infoportugal.impresa.pt> wrote:
>
> Hi,
>
> I have trying using the topology to correct some data with marginal errors
> and in some particular cases i'd like to use a higher snap tolerance than
> the defined in the topology.
> The topology has a tolerance of 0.01m (using a metric projection) and some
> lines need an higher tolerance of 0.1m to be fixed. Here's the code i used
> to create the topology and to fix the particular cases:
>
> SELECT topology.CreateTopology('a_topology', 3763, 0.01, true);
>
> UPDATE lines_table
> SET topo = topology.toTopoGeom(geom, 'a_topology', 1, 0.1)
> WHERE id = 1263;
>
> Even though the line is closer than 0.1m to another line, it isn't
> snapped. Am i thinking wrong here? Shouldn't the line be snapped? Which of
> the tolerances prevails?
> If this is the expected behaviour is there a better way to do what i'm
> trying to do?
>
> Thanks in advance,
>
> Alexandre Silva
>
>
>
>
> _______________________________________________
> postgis-users mailing list
> postgis-users at lists.osgeo.org
> https://lists.osgeo.org/mailman/listinfo/postgis-users
> <https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.osgeo.org%2Fmailman%2Flistinfo%2Fpostgis-users&data=02%7C01%7Camsilva%40infoportugal.impresa.pt%7C993cd4fd7266463c411908d81c7eb1b3%7Cd227b2e71c404f63b5132f3665c334e6%7C0%7C1%7C637290677762167348&sdata=mFfo8W%2F%2BQ3nQJOyoE5OjvDro%2Fgrj4BgdkMapg58vs4s%3D&reserved=0>
>
> _______________________________________________
> postgis-users mailing list
> postgis-users at lists.osgeo.org
> https://lists.osgeo.org/mailman/listinfo/postgis-users
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/postgis-users/attachments/20200701/2c9a4508/attachment.html>