How does spatial referencing information get carried over in .dwg format?

[PatrickMoulden]

How does spatial referencing information get carried over in .dwg format when exporting out of a .mxd?

My reason for asking is that I recently been having issues with data exported from ArcMap to CAD (Export to CAD tool) and having the receiving CAD tech claim that the resulting DWG file comes in with no projection or coordinate system.  I do not have CAD software on my computer so it is difficult to investigate exactly what is going on.

The ESRI help resources that I found on this topic seem to focus more on bringing CAD data into ArcMap.

[BrettHill]

See this help page.

http://resources.arcgis.com/en/help/main/10.1/#/About_CAD_dataset_spatial_references/00100000007t000...

To read the embedded spatial reference the CAD tech will need to install ArcGIS for AutoCAD.

[KarenHodge · Accepted solution]

I'm going to guess that your CAD tech is using AutoCAD Map 3d.  Map 3d includes a proprietary method of storing coordinate systems in the drawing.  Export to CAD cannot populate the drawing coordinate system in a way that Map 3d understands.  It does, however, embed a coordinate system in the drawing that can be used by ArcGIS for AutoCAD--which will run with Map 3d.

There are many clever ways a LSP programmer one could read the embedded coordinate system and then convert it to a Map3d coordinate system.  But it may be easier to just tell your tech which coordinate system should be used.


Here's another workaround:
Have your CAD technician create an empty DWG file with the Map 3d coordinate system embedded in it.  Create a separate file for each coordinate system you use regularly.  Then, when you use the Export to CAD tool, you can set the correct DWG as the seed file for the output.

It will be up to you, however, to select the right seed file to match your MXD.

Hope this helps.

--Karen

How does spatial referencing information get carried over in .dwg format when exporting out of a .mxd?

My reason for asking is that I recently been having issues with data exported from ArcMap to CAD (Export to CAD tool) and having the receiving CAD tech claim that the resulting DWG file comes in with no projection or coordinate system.  I do not have CAD software on my computer so it is difficult to investigate exactly what is going on.

The ESRI help resources that I found on this topic seem to focus more on bringing CAD data into ArcMap.

[PatrickMoulden]

Thanks for the tips! I will definitely try the workaround with the empty DWG file.  However, since this issue spans multiple companies with different CAD and GIS techs involved in each organization (I am the lead GIS Analyst and DbM for this project) I might be better off hiring a LSP programmer or even learning the language myself than trying to explain the project's custom coordinate system to the ever changing list of people involved. 

I have started to push ArcGIS for AutoCAD, (going as far as to have every new CAD machine that we build have it installed).  However, do to some compatibility issues with different CAD software versions and the fact that even within my organization some of the CAD techs can be very reluctant to adapt new technologies, progress in getting it widely used is somewhat slow.