[postgis-users] break lines at intersections

[Stephen V. Mather]

Also, ST_DWithin is a bounding box test, so it’s fast but not accurate.
You’ll want to do a second test with ST_Distance to get the actual distance
after gathering up everything that results in true for ST_DWithin.

 

Best,

Steve

 

http://www.clemetparks.com/images/esig/cmp-ms-90x122.pngStephen Mather
Geographic Information Systems (GIS) Manager
(216) 635-3243

svm at clevelandmetroparks.com
 <http://www.clemetparks.com/> clevelandmetroparks.com

 

 

 

 

From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Pedro
Costa
Sent: Thursday, May 17, 2012 11:54 AM
To: PostGIS Users Discussion
Subject: Re: [postgis-users] break lines at intersections

 

i found the error. the parallels are a less then 3 meters...

thanks



Em 17-05-2012 16:43, Pedro Costa escreveu: 

I'm already tried this function but with no good results, I do not
understand why.
You can see an example in the attached image. The streets are red lines. The
parallel purple and what I want to clear yellow.

Any idea ?


I tried the st_dwithin like this:


create table street8 as (SELECT paralell.geom FROM parallel,street WHERE
st_dwithin(paralell.geom, streets.the_geom, 2.99 ))


The 'line erros' that i want to delete are a less than 3 meters from
streets...


thanks



Em 17-05-2012 16:32, Nicolas Ribot escreveu: 

Yes, it should be: 

st_dwithin will help you to find all lines from a table within a certain
distance to other lines.

 

Nicolas

 

On 17 May 2012 17:23, Pedro Costa <pedrocostaarma at sapo.pt> wrote:

Great Nicolos, works...

It is possible select lines from one table a less than 3 meters from lines
from another table?and delete them...

thanks


Em 17-05-2012 15:41, Nicolas Ribot escreveu: 

Hi Pedro, 

 

select (st_dump(st_union(geom))).geom from lines;

 

will cut your network of lines at intersections.

 

Nicolas

On 17 May 2012 11:57, Pedro Costa <pedrocostaarma at sapo.pt> wrote:

does anyone know how I can cut the lines at intersectionslike the image
attached?

I can´t install postgis 2.0 for now....

I see a few examples with st_union and st_dump but i don't understand...


Thanks

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