Opened 13 years ago

Last modified 6 years ago

#636 new defect

r.thin creates triangle at acute intersection of two lines

Reported by: needelsd Owned by: grass-dev@…
Priority: normal Milestone: 6.4.6
Component: Raster Version: 6.4.0 RCs
Keywords: r.thin, r.to.vect Cc:
CPU: OSX/Intel Platform: MacOSX

Description

I have rasters that were generated using v.rast followed by r.buffer. Using r.thin on such a raster occasionally creates a triangle at an intersection instead of the expected two intersecting lines. All of the examples I have seen involve relatively acute angles (less than 25 degrees??).

This result is easily seen by using r.to.vect to create a vector, which then needs v.clean to remove dangles. I have attached a screenshot that shows the original (fat) raster in magenta, the vector with dangles in white, and the cleaned vector as (a thinner) green. There are numerous acute angles that generate the vectors I would expect, with one exception in the center.

Attachments (1)

r.thin.png (12.7 KB ) - added by needelsd 13 years ago.
Vectors created using r.thin, r.to.vect, and v.clean

Download all attachments as: .zip

Change History (3)

by needelsd, 13 years ago

Attachment: r.thin.png added

Vectors created using r.thin, r.to.vect, and v.clean

comment:1 by hamish, 13 years ago

Keywords: r.to.vect added

I think this is really a r.to.vect issue and not a r.thin one.

I am not sure if there is a correct solution though. i.e. this could be a (desired in some cases) feature, not a bug.

to remove the undangles maybe v.to.db upload line length then v.extract where line length > some threshold?

Hamish

comment:2 by neteler, 6 years ago

Milestone: 6.4.06.4.6
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