February 26, 2008

Import From CAD and Chainsaws

When someone is talking on their cell phone in the car and you’re riding along, you really can’t help but eavesdrop on the conversation, albeit one-sided. I recently heard this from a friend of mine while talking with his 8yr old son on the phone:

…Did you get all the leaves picked up? ...How about sweeping the back porch? ...and the grass?.... the what?, …why? ... No buddy, you don’t need a chainsaw for that!
The girls in the back seat immediately tuned in at that last exchange. His sister quickly asked, “Chainsaw?! What is Riley doing with a CHAINSAW?!”

The right tool for the job may be less powerful and simpler than the one I might first think. There is a geoprocessing tool in ArcGIS called Import from CAD. Judging by its name, many people gravitate to the tool to make use of CAD files in ArcGIS. Its original design was to generate a normalized view of a CAD file for dissecting and reassembling into all manner of difficult and sophisticated workflows. However for most purposes it is more than overkill, it is much more work than simply opening and using a CAD file directly.

ArcGIS reads CAD files as GIS content and the process of Importing is not necessary. I can create GIS data sets like Shapefiles, or Geodatabases simply by opening a CAD file and copy-and-pasting or, using any number of tools that copy data such as Copy Features, Merge, Append, Feature Class to Feature Class, etc…

The Import From CAD tool creates a Staging Geodatabase that is a highly normalized set of tables that mimics the actual internal organization of a CAD file. The imeadiate result is less directly usable than the default CAD feature classes created by ArcGIS when it opens a CAD file. In fact when I do use the Import From CAD tool the first thing I usually look to do is link the tables together in a useful way, then create a subset of the data, and copy that data to a Geodatabase. Opening up a CAD file and using the Feature Class to Feature Class tool does that for me in a single step.

Import from CAD is a tool that does handles SPLINE geometry better than the default CAD file direct read, and can access AutoCAD Extended Entity Data. However, if I am not working with this type of data there is little reason for me to bother with the tool.

In like manner, just because a chainsaw can make short work of a rose bush, it may be just a little overkill, resulting in even more pieces for me to pick up after I’m done.


Anonymous Anonymous said...

This is very interesting tool, but do you know if its possible do the same as this tool using arcobjects with ArcGIS Server.

I need to develop a tool to import Cad files (with XData) to SDE-Oracle database and i don't know if it is possible or not...

Thanks in advance!!

3:07 AM  
Blogger Don Kuehne said...

It is my understanding that you can access and execute any geoprocessing tool. You could also execute a script that has a tool in it to run it. From there you could use other ArcObjects directly to peice together the XData in a useable format. This usually requires that you pivot the resulting XData table found in the output CAD Staging Geodatabase created by the IMPORT FROM CAD tool.

3:59 PM  

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