<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div dir="ltr"></div><div dir="ltr">Thanks Micha,</div><div dir="ltr"><br></div><div dir="ltr">That will be very useful. I figured out the vertex thing later by manually adding one. I thought the QGIS snapping tool would do that but it looks like the QGIS tool tolerance looks for the nearest vertex but not the nearest line. Grass v.clean will be very useful. </div><div dir="ltr"><br></div><div dir="ltr">I will make a bug report for the QGIS tool as the option selected should have added a vertex IMHO.</div><div dir="ltr"><br></div><div dir="ltr">Nicolas</div><div dir="ltr"><br>Le 9 mai 2019 à 05:33, Micha Silver <<a href="mailto:tsvibar@gmail.com">tsvibar@gmail.com</a>> a écrit :<br><br></div><blockquote type="cite"><div dir="ltr">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<p>I made a map showing the vertices on each line, and it's clear
that the snapping of line ID 13232 and line 13227 did not create a
new vertex at the intersection. Have a look at the left hand image
in the attached file.</p>
<p> <br>
</p>
<p>I tried the v.clean module GRASS, instead and the new vertex was
correctly created (right hand image in the attached)<br>
</p>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"><tt>v.in.ogr
3D_RiverNetwork_RiversLakes_SingleLines_190508_ExampleOfSnapProblem.shp
output=river_network key=ID --o</tt><tt><br>
</tt></div>
<div class="moz-cite-prefix"><tt>v.clean river_network
out=river_network_clean error=dummy tool=snap,break thresh=20
--o</tt><tt><br>
</tt></div>
<div class="moz-cite-prefix"><tt>v.out.ogr --o river_network_clean
format=ESRI_Shapefile out=river_network_clean.shp</tt></div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">After the v.clean operation the report
showed one additional vertex, more than the original. <br>
</div>
<div class="moz-cite-prefix">My guess is that if there is no vertex
within the threshold snapping distance then a new vertex is <b>not
created. </b>The GRASS module, on the other hand, creates new
vertices (and also saves to an "error" vector map).</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">Regards,</div>
<div class="moz-cite-prefix">Micha<br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"> <br>
</div>
<div class="moz-cite-prefix">On 08/05/2019 21:40, Nicolas Cadieux
wrote:<br>
</div>
<blockquote type="cite" cite="mid:3f0d0cde-aa57-9b64-a1a2-8ad6a24b1ac6@archeotec.ca">Hi,
<br>
<br>
Included is a small section of the network with the underlying
problem.
<br>
<br>
Nicolas
<br>
<br>
On 2019-05-08 1:53 p.m., Nicolas Cadieux wrote:
<br>
<blockquote type="cite">Hi,
<br>
<br>
I am working on a network of rivers.
<br>
<br>
I have singlepart lines (shape file) that appear snapped in
QGIS. I even forced the lines to snap using the « snap
Geometries to layer » tool. (Using the same line layer as both
input layer and Reference layer using a 10m tolerance ).
(Behaviour is set to the topmost option.) Some lines have been
snapped using this method but not all.
<br>
<br>
When I zoom in, I cannot see that the line are not snapped. But
when I use Python Shapely module to count the interesecting
geometries on the end nodes, some snapped node in the middle of
the network appear to be intersecting with only one geometry
(and not two or more). This seems to be confirm by the spatial
selection tool in QGIS also.
<br>
<br>
How could this be?
<br>
<br>
Is there a different tolerance to what is considered a snapped
line in different software?
<br>
<br>
How else can I find lines that are not snapped in QGIS?
<br>
<br>
A penny for your thoughts!
<br>
Nicolas
<br>
<br>
Qgis3.6.2 on Windows X
<br>
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<pre class="moz-signature" cols="72">--
Micha Silver
Ben Gurion Univ.
Sde Boker, Remote Sensing Lab
cell: +972-523-665918</pre>
</div></blockquote><blockquote type="cite"><div dir="ltr"><river_network.png></div></blockquote></body></html>