v.clean break apparently does not work

[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.

[neteler]

Please provide sample data.

[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.

[mmetz]

Replying to 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 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

[neteler]

Looks like solved?

[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.