To make our drawings work from AutoCad Map 3D in QGIS, we make sure that our drawings have coordinate system assigned (even though we only use 1 coordinate system in particular, so it is kind of pointless). Then we save either as DXF or export them as to shapefiles.

If we do the export to shapefile we also make sure it is the right coordinate system, that is why we also do a conversion, even though it is the same coordinate system we convert to.

But the thing is (rather is a DXF or shapefile does not matter) even though we clearly assigned it the correct coordinate system and when we load it in a project, . QGIS still is confused and thinks the coordinate system is invalid. We have to manually assign the coordinate system again. The shapefiles are on the location as they should be, but considering these shapefiles/DXF files need to be Lambert 72 standard. This is kind of annoying.

Why does this happen? Does AutoCAD Map 3D not save a coordinate file or something?

  • you can avoid that by setting a default crs in QGIS - whenever you load a layer with an unknown crs, QGIS defaults to the one you told it to use – sn1ks Sep 23 '20 at 11:38

AutoCAD drawings and DXF files do not have an additional coordinate file. The features in those files have an X and Y coordinate, those coordinates could be meters, feet, degrees, etc. I would continue with setting the correct coordinate system when you load the relevant DXF files into Qgis.

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