I came across a strange issue when exporting a polygon layer from AutoCAD Civil 3D to a shapefile.

The original AutoCAD drawing looks like this:

enter image description here

When loading it in to QGIS it looks correct:

enter image description here

But when I uploaded it to the GeoServer I got issues with the middle polygon (fully black). It looked like it moved a little to the south. Trying so solve this in QGIS I re projected it to a WGS84 layer (originally UTM 33N) but the problem stayed :

enter image description here

After extracting vertices I noticed the vertices of the middle polygon where the same for both layers so it had to bend?!

I did solve the problem by making a merged polygon layer (1 single polygon) of all the polygons in the shape file. Making a difference of it with a shapefile without the middle polygon and merging this with the shapefile without the middle polygon.

  • can you check the polygons are valid in QGis before and after saving to shapefile - that looks like an inside out polygon. – Ian Turton Feb 12 at 13:50

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