topology checker misleading errors

[qgib]

Author Name: Giovanni Manghi (@gioman)
Original Redmine Issue: 13296
Affected QGIS version: 2.8.3
Redmine category:c++_plugins/topology_checker

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When digitizing adjacent polygons using the "avoid intersection" rule, is easy enough at some point (especially if the layer is reprojected) to get gaps or overlapped areas... at least the topology checker says so. A further check, with GRASS, seems to exclude this problems, as holes (gaps) and overlapping areas are not detected.

[qgib]

Author Name: Thomas Nogatz (@TomNog)

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Could you describe please how you did check the layer with GRASS?

[qgib]

Author Name: Giovanni Manghi (@gioman)

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Thomas Nogatz wrote:

Could you describe please how you did check the layer with GRASS?

you have to import your vector into a GRASS mapset/location. You can do it using native GRASS or you can also use the QGIS/GRASS plugin (also to create a new mapset/location). The import module is v.in.ogr and you should use in first place without using any snapping option. After importing the vector you may end with up to 3 different GRASS layers: 0, 1, 2.

1 is the "normal" layer as you would expect
0 is a layer with polygons representing the holes/rings/spaces in the original layer
2 is a layer with polygons representing the overlapped areas in the original layer

if after the import you end up with just the 1 layer, then your original layers has no holes/rings/spaces and no overlapping areas.

[qgib]

Author Name: Giovanni Manghi (@gioman)

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• easy_fix was configured as 0
• regression was configured as 0

[qgib]

Author Name: Giovanni Manghi (@gioman)

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End of life notice: QGIS 2.18 LTR

Source:
http://blog.qgis.org/2019/03/09/end-of-life-notice-qgis-2-18-ltr/

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• resolution was changed from to end of life
• status_id was changed from Open to Closed