4

I'm using OMBB in QGIS 3.10. Most of polygons are processing correctly, but there are some, which seems to be processing wrong:

sample

But if rotate layer a little - result will be more correct:

enter image description here

SRS - EPSG:3857.

What I'm doing wrong? Maybe problem is related with this?

UPD:

Add conflictive feature in wkt:

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Improve this question
6
  • 1
    How do you define the correctness of the result?
    – user30184
    Dec 25, 2019 at 21:28
  • 2
    I was doing some tests since the referred question was asked. Seems to be a bug with the geometry vertex coordinates when they are rounded to integers. Please, Extract by selection just the conflictive feature, make a Convex hull, and for the output layer include in the question the output of a geom_to_wkt($geometry,3) expression. Test making a Buffer of some decimal (e.g., 0.0123) radius and try the Oriented Minimum Bounding Box to the buffered layer. Source code is in line 957 of qgis.org/api/qgsgeometry_8cpp_source.html.
    – Gabriel De Luca
    Dec 26, 2019 at 2:47
  • @GabrielDeLuca Thanks, trick with buffer is working! Sample of conflictive feature added in post.
    – Алексей Трошин
    Dec 26, 2019 at 6:36
  • You are welcome. Your geometry does not have its coordinates rounded to meter. I can't understand where is the problem but I think that this is a bug.
    – Gabriel De Luca
    Dec 26, 2019 at 10:05
  • OpenJUMP seems to create a good minimum bounding box out-of-the-box POLYGON (( 6264704.943593819 8041903.205278208, 6264698.644892796 8041924.624800196, 6264668.747276492 8041915.833000495, 6264675.045977515 8041894.413478508, 6264704.943593819 8041903.205278208 )).
    – user30184
    Dec 26, 2019 at 14:39

1 Answer 1

Reset to default
1

The issue has been fixed with PR github.com/qgis/QGIS/pull/34334 since QGIS 3.12. Thanks Andrea for the update.

The oriented minimum bounding box calculated by QGIS 3.16 for the given polygon is:
Polygon ((6264704.93729321844875813 8041903.20301713142544031, 6264698.6385921984910965 8041924.62253911606967449, 6264668.74097589403390884 8041915.83073944505304098, 6264675.03967691399157047 8041894.4112174604088068, 6264704.93729321844875813 8041903.20301713142544031))

I have reported an issue on this in the following link: https://github.com/qgis/QGIS/issues/33532. At the moment, a workaround is to change the coordinates of the vertices of the geometry.

This can be done by reprojecting the layer to another coordinate system, or by applying a minimal decimal buffer over the geometry of the problematic features.

Improve this answer
1
  • 1
    The issue has been fixed with PR github.com/qgis/QGIS/pull/34334 since QGIS 3.12. The oriented minimum bounding box calculated by QGIS 3.16 for the given polygon is: Polygon ((6264704.93729321844875813 8041903.20301713142544031, 6264698.6385921984910965 8041924.62253911606967449, 6264668.74097589403390884 8041915.83073944505304098, 6264675.03967691399157047 8041894.4112174604088068, 6264704.93729321844875813 8041903.20301713142544031))
    – Andrea Giudiceandrea
    Mar 17, 2022 at 12:23

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