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What is the best method of importing/exporting dxf files with QGIS ? I work in an engineering field and we use CAD and specialist design programs, and often go through several iterations during a project.

I am having trouble interchanging data between QGIS and dxf formats. I export several layers from QGIS in DXF format and load them into cad. Essentially I xref the exported DXF files into cad, and then draw over the top of them in cad, as I find it quicker and more acruate. The files line up ok, but need to be scaled and transformed to match the coordinates in QGIS. I then detach the xref's, save the new DXF with line work on a single layer. The DXF file coordinates match the qgis coordinates.

I cant seem to get the new DXF to import back into QGIS. I would like to be able to export and import a particular data table several times as the project develops.

Screenshot 1 - I exported the pink polygons and edited them in CAD. I then imported the DXF file back in but nothing came in - see "entities".

enter image description here

Screenshot 2 - Attribute table of imported layer.

enter image description here

Thanks

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Getting used to QGIS editing tools will be less painful than changing back and forth between GIS and CAD. –  underdark May 15 '12 at 11:47
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@boberdorf, why do you need to export and import so many times? Data interchange between between cad and gis isn't pratical because they have different nature. –  Pablo May 15 '12 at 12:07
    
For shape editing, like the images shown, going back and forth between CAD seems cumbersome. However, if you are drawing building footprints and other orthogonal or complex lines, having the advanced drawing tools available in CAD packages makes a lot of sense. Especially if you are using QGIS for modeling and need those speculative footprints as part of your analysis. –  afwatl May 18 '12 at 15:36
    
ah, well I just discovered the cadtools python plugin. It seems to offer a lot of CAD functionality. You can find it in the CatAIS repository. However, that doesn't really answer your question, and I would like to know if there is a good way to go back and forth and preserve scaling, etc. –  afwatl May 18 '12 at 16:07
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4 Answers

For dxf file I use OpenJump or gvSIG - gvSIG CE and not QGIS

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I have been using mmqgis plugin with some success for transfer / export as csv with geometry.

The dxf format from the cad system which is suitable for import seems to be 2004-2006, coming into QGIs as a delimited text layer. Obviously I use a UTM coordinate system. For a polygon it will export two files, one is the attribute table.

To install mmqgis, you may have to hunt around in the plugin system a little.

The main challenge I expect is that cad exports have so many options for the management of blocks, text etc.

See also my other answer at;

http://gis.stackexchange.com/a/32761/6264

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if you can/want to share the type of change that usually run in the CAD environment ... we try to assess the feasibility in Qgis enviroment.

Good work!

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One option if you use autodesk is to use the mapimport/mapexport commands to convert from dxf to shp and from shp to dxf. This will give you the option to keep the data objects if needed. This way you can edit shp in GIS and edit dxf in CAD.

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