Using the Import From CAD tool
Release 9.2 Last modified August 15, 2007	Print all topics in : "Geoprocessing tools for CAD translation"

About using the Import From CAD tool

The Import From CAD tool is generally for more sophisticated solutions when creating your own custom translations. This tool recasts native CAD files into feature classes and a series of tables. This is called a staging geodatabase, which is intended to be a staging area from which custom feature classes will be created. It is recommended that new custom feature classes be written to an alternative location and leave the staging area unmodified. This preserves the staging geodatabase to create new custom feature classes, since the data has not been modified.

The staging geodatabase is a flattened structure of the CAD file recast as a GIS geodatabase. With the flattened structure, you are given the flexibility to reconstruct your own custom feature classes. Each piece of geometry translated from a CAD file will have multiple attributes that can be associated with it. A single line could have the obvious entity table attributes and layer-by-layer information about the same piece of geometry in the CadLayer table. This illustrates how joining multiple tables to a single set of features is often needed. There are key-named fields that can be used to join the geometry to the attributes.

Fields such as EntID and ObjectID can be used for the joins and allow the geometry to get the attribute information needed to minimize the data loss during this semantic translation process, for example, by joining the Point feature class with the Txt Prop table to get the text value with the point locations. By joining the tables to the feature classes, you are constructing your own custom translations to create user-specified feature classes. The Import From CAD tool adds a level of complexity but allows more low-level control.

This process of joining feature classes may be more involved than what you require, so it is reasonable to use the CAD feature dataset. These CAD feature classes are similar to the staging geodatabase, except all the information and the geometry has been joined. Think of the CAD feature classes as an ESRI-enforced schema that joins features with attribute information.

How to use the Import From CAD tool

1. Start ArcCatalog.
   
2. Open the toolbox window and choose the Import From CAD tool in the Conversion toolbox.
   
3. Execute the Import From CAD tool on the CAD files that need to be converted to ArcGIS features.
   

The staging geodatabase can now be used to create custom feature classes that always use the staging geodatabase as the starting point. Now you need to use ModelBuilder to create a semantic translation workflow.


4. Create a toolbox in a directory of your choice, then create a new model.
   
5. Add the staging geodatabase as input in this model.
   
6. Drag in the Select Data tool and from the same input, select the polyline as the child data element.
   
7. Add the Make Feature Layer tool to ModelBuilder and connect it to the output of the Select Data tool added in the previous step.
   
8. Add another Select Data tool and select the entity table child data element.
   
9. Drag the Select Data tool again and from the same input, select the polyline as the child data element.
   

The Select Data tool selects the appropriate table and feature class that will be joined. The Make Feature Layer tool creates an in-memory feature layer from the input, which allows the manipulation of the feature class in the current ArcGIS session.


10. Drag the Add Join tool onto the ModelBuilder window and connect the two branches of the existing model.
    
11. Open the Add Join tool and use the EntID field as the common field on which to join both parameters.
    
12. Drag the Select tool and connect the output of Add Join to Select.
    
13. Open the tool and use the Expression parameter to select a subset of features to be output.
    

The Add Join tool performs a join based on the key-named field that is used to join the geometry with the attributes from the staging geodatabase. The Select tool is used to pull a subset of the features and create a custom feature class that contains only the elements that are needed.

Tip

If you're working with a single CAD file that needs to be converted to a feature class, consider using tools such as Make Feature Layer and Copy Features. If there are a number of CAD files that need to be translated to a geodatabase, consider Import From CAD, since it can take in multiple CAD files.

Please visit the Feedback page to comment or give suggestions on ArcGIS Desktop Help.
Copyright © Environmental Systems Research Institute, Inc.