[GRASS-dev] [GRASS GIS] #1595: v.clean break apparently does not work

#1595: v.clean break apparently does not work
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Reporter: pcav | Owner: grass-dev@…
     Type: defect | Status: new
Priority: normal | Milestone: 6.4.3
Component: Vector | Version: 6.4.1
Keywords: | Platform: Linux
      Cpu: x86-64 |
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v.clean input=patched@paolo type=line tool=snap,break,rmdupl,rmsa
thresh=1,0,0,0 output=patched_1

The lines are not broken.

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Ticket URL: <http://trac.osgeo.org/grass/ticket/1595&gt;
GRASS GIS <http://grass.osgeo.org>

#1595: v.clean break apparently does not work
--------------------+-------------------------------------------------------
Reporter: pcav | Owner: grass-dev@…
     Type: defect | Status: new
Priority: normal | Milestone: 6.4.3
Component: Vector | Version: 6.4.1
Keywords: | Platform: Linux
      Cpu: x86-64 |
--------------------+-------------------------------------------------------

Comment(by neteler):

Please provide sample data.

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Ticket URL: <http://trac.osgeo.org/grass/ticket/1595#comment:1&gt;
GRASS GIS <http://grass.osgeo.org>

#1595: v.clean break apparently does not work
--------------------+-------------------------------------------------------
Reporter: pcav | Owner: grass-dev@…
     Type: defect | Status: new
Priority: normal | Milestone: 6.4.3
Component: Vector | Version: 6.4.1
Keywords: | Platform: Linux
      Cpu: x86-64 |
--------------------+-------------------------------------------------------

Comment(by pcav):

Sample location here:
http://int.faunalia.it/~paolo/test.tar.gz

See also this thread:

http://lists.osgeo.org/pipermail/grass-user/2012-January/063306.html

Thanks.

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Ticket URL: <http://trac.osgeo.org/grass/ticket/1595#comment:2&gt;
GRASS GIS <http://grass.osgeo.org>

#1595: v.clean break apparently does not work
--------------------+-------------------------------------------------------
Reporter: pcav | Owner: grass-dev@…
     Type: defect | Status: new
Priority: normal | Milestone: 6.4.3
Component: Vector | Version: 6.4.1
Keywords: | Platform: Linux
      Cpu: x86-64 |
--------------------+-------------------------------------------------------

Comment(by mmetz):

Replying to [ticket:1595 pcav]:
> v.clean input=patched@paolo type=line tool=snap,break,rmdupl,rmsa
> thresh=1,0,0,0 output=patched_1
>
> The lines are not broken.

The vector 'patched' is the result of patching a 2D vector (region) with a
3D vector (contour). The lines are not broken because there are no
intersections in 3D space, only in 2D space. You need to transform the z
coordinates of either the contour vector or the patched vector to be all
zero with v.transform zscale=0, then the lines are broken.

About the other problem described in the thread in comment [comment:2],
how to snap bad polygons to good polygons, this is now possible with
v.overlay, using the good polygons as ainput and the bad polygons as
binput with operator=or. The snapping threshold may need to be set to some
larger value than default=1e-8.

Markus M

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Ticket URL: <https://trac.osgeo.org/grass/ticket/1595#comment:3&gt;
GRASS GIS <http://grass.osgeo.org>

#1595: v.clean break apparently does not work
---------------------+------------------------------------------------------
Reporter: pcav | Owner: grass-dev@…
     Type: defect | Status: new
Priority: normal | Milestone: 6.4.3
Component: Vector | Version: 6.4.1
Keywords: v.clean | Platform: Linux
      Cpu: x86-64 |
---------------------+------------------------------------------------------
Changes (by neteler):

  * keywords: => v.clean

Comment:

Looks like solved?

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Ticket URL: <https://trac.osgeo.org/grass/ticket/1595#comment:4&gt;
GRASS GIS <http://grass.osgeo.org>

#1595: v.clean break apparently does not work
---------------------+------------------------------------------------------
Reporter: pcav | Owner: grass-dev@…
     Type: defect | Status: new
Priority: normal | Milestone: 6.4.3
Component: Vector | Version: 6.4.1
Keywords: v.clean | Platform: Linux
      Cpu: x86-64 |
---------------------+------------------------------------------------------

Comment(by pcav):

Thanks for the clarification.
I'd suggest to either:
* check about 3D-2D in input layer, and warn the user about probable empty
intersection, or
* flatten out 3D layers (warning the user) in case of 2d-3D mixup.
Thanks.

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Ticket URL: <https://trac.osgeo.org/grass/ticket/1595#comment:5&gt;
GRASS GIS <http://grass.osgeo.org>