How To: Control exported CAD properties using a lookup table
Instructions provided describe how to use a lookup table joined to a feature class as input to the Export to CAD tool to specify the color, layer, line style and other CAD layer or entity properties of the output CAD file.
The Export to CAD tool creates CAD drawings from feature classes. When the feature classes include specially named fields, such as CAD property fields, the values in those fields modify the behavior of the Export to CAD tool. Export to CAD symbolizes and formats the output CAD drawings according to those values in the specially named columns.
The Export to CAD tool recognizes these specially named fields in the feature attribute table or in a joined table. It is useful to create a lookup table when adding fields to a feature class is not desirable, or when is not possible. For example, with read-only data sources.
Use this technique to create different CAD files according to multiple CAD drawing standards, using the same feature classes and without modifying the feature classes themselves.
- Determine how the lookup table records should link to the exported features. Using an existing field, such as a domain sub-type or other distinguishing attribute, is a logical field to base the join of the lookup table, which depends on the desired output result.
Alternatively, create and populate a custom specific feature table key field to control the CAD symbology for various features according to custom methods.
A column is required in each field with common values upon which to join the two tables.
- Create the lookup table using the Create Table tool. Arctoolbox > Data Management > Table > Create Table.
To assist in the creation of the lookup tables, use the Frequency tool: ArcToolbox > Statistics > Frequency. It creates a table that includes unique occurrences of values for a given field in a feature class.
- Add the specially named CAD property fields to the lookup table. Use the Add CAD Fields conversion tool, or use the Add Field data management tool to do this. Be careful to specify the correct field type and to name the CAD fields correctly.
The CAD fields included in the lookup table depend on how the CAD file is to be created. To support a simple CAD layering standard, use a lookup table that contains just the CAD layer names in a field called 'LAYER'.
It may be necessary to be more specific about individual entity color, entity type, line style, and so forth. If so, add and populate those CAD property fields in the lookup table.
- Create a separate record in the lookup table for each unique value of the key field contained in the feature class. Populate the table with all of the unique combinations of CAD symbology to be created by the Export to CAD tool.
- Join the feature class to the lookup table. Create an ArcMap feature layer from the feature class that contains a join by right-clicking on the ArcMap Table of Contents and selecting Joins and Relates > Joins.
Alternatively, create a geoprocessing script or model that performs the join using the Make Feature Layer and Add Join tools.
- Use the feature layer with the joined lookup table as input to Export to CAD. The Export to CAD tool recognizes the specially named CAD property fields in the lookup table and creates the CAD entities according to the values contained in the table.
Once the CAD symbology standard has been encoded in the lookup table, use the lookup table as often as needed with different feature classes to create drawings according to that standard.
Create different lookup tables for use on the same exported feature classes to create CAD drawings according to different CAD standards.