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Fix: Flatten OGR curve geometries (CurvePolygon) to polygons before import #2460

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Fix: Flatten OGR curve geometries (CurvePolygon) to polygons before import #2460

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11 changes: 10 additions & 1 deletion src/gdal/ogr_file_format.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1059,7 +1059,16 @@ void OgrFileImport::importLayer(MapPart* map_part, OGRLayerH layer)
++empty_geometries;
continue;
}


if (OGR_G_HasCurveGeometry(geometry, 1)) {
OGRGeometryH linear_geom = OGR_G_GetLinearGeometry(geometry, 0, nullptr);
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@dg0yt dg0yt Jan 6, 2026

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"The ownership of the returned geometry belongs to the caller."

if (linear_geom) {
OGR_F_SetGeometryDirectly(feature.get(), linear_geom);
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@dg0yt dg0yt Jan 6, 2026

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"this function assumes ownership of the passed geometry" ✔️

geometry = linear_geom;
}
}

OGR_G_FlattenTo2D(geometry);
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@dg0yt dg0yt Jan 6, 2026

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IIUC this is not directly related to curve geometries: "converts all Z coordinates to 0.0." Is there an actual benefit from this operation for further processing in Mapper?

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@jirivis jirivis Jan 8, 2026

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Hello Kai,
I think that Mapper is working in 2D only? There are (not exactly in Czech) some base maps in 3D, and I think that Mapper can not import these 3D "polygonZ" features for this reason. I think that there would be some ways to import these features into Mapper. Please check the code that I sent. It is from Gemini, I am not a programmer (-:
Yes, I think that curve geometries and "polygonZ" features are two different problems.
Excuse my amateurism.

importFeature(map_part, feature_definition, feature.get(), geometry, clipping.get());
}
}
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