[GIS] Transforming from DWG/DXF to GIS

Question

I've got tons of DWG/DXF files with information (in several layers) dealing with:

• Contour lines and elevation (lines)
• positions of antennas (points)
• protection areas (polygons)
• administrative boundaries (lines)
• roads (lines)
• rivers (lines)
• fences (lines)
• …

All this information have been inserted into these CAD files in a non-standard way (not-unified names or colors in layers), and now I want to translate it into GIS (SHP files or into a PostGIS Server).

I'm investigating how to translate these data.

I'm considering:

• create GDAL scripts with Python (http://www.gis.usu.edu/~chrisg/python/2009/)
• create scripts with Teigha libraries (http://www.opendesign.com/guestfiles/TeighaFileConverter)
• use ArcGIS Desktop (with Python scripts) (http://www.slideshare.net/cageyjames/python-scripting-with-arcgis)
• use QGIS or gvSIG (http://www.qgis.org/, http://www.gvsig.org)
• use GlobalMapper (http://www.globalmapper.com/)
• use GeoKettle (http://www.spatialytics.org/projects/geokettle/)
• …

Can CAD2GIS translation be achieved with this software?

Answer 1

It seems to me that the main problem for you is to introduce some order to your tons of DWG/DXF files with information (in several layers).

Regardless of choosing software/tool I can recommend you to describe your data. Here is some thoughts:

1. You should develop some kind of unique codes for all types of your features. It can be one attribute or several or some other way. Let's say it will be some dictionary of codes. PS it is very possible that you already have such dictionary.
2. You need to make description of your input data based on its properties (layer name, color, linestyle, line width, etc) to be able to pick any object from DWG, read it's properties, then search you description document, find matching record and assign code (of matching description) to your input feature.
3. Prepare such description in some table format (i.e. Excel).
4. Write script which will loop through all your input data, match it's properties to Description, assign code and save it to appropriate featureclass/SHP/table.

In such way you can easily update such documented description in future and apply it again to any data without need to modify your scripts.

My experience:

We usually prepare such descriptions in XLS file (it can be easily edited by any cartographer or technician) and use FME for transforming and converting data. But I think you can implement similar idea with any software which can read DWG with properties of objects.