Export features to specific CAD layers

Summary

Note:
This article pertains to retired ArcGIS versions 9.x only. Later versions of ArcGIS may contain different functionality, as well as different names and locations for menus, commands and geoprocessing tools.

Instructions provided describe how to create a CAD file where ArcGIS features are exported to specific CAD layers using the Export to CAD geoprocessing tool. Using this technique in combination with a seed file with predefined layer symbology provides a simple means of supporting the export of ArcGIS data using a CAD Layering Standard.

Procedure

This procedure uses the Export to CAD geoprocessing tool's extended functionality to control the CAD layer by including a specially named field in the output feature class. When a feature class contains a field that is named, aliased or renamed in a geoprocessing model to the name ('Layer'), valid values in that field are used to control the destination CAD layer name of each exported CAD entity.

It is often useful to populate the feature classes' 'Layer' field with existing layer names that are already included in a CAD seed file. In this way, exported entities can take advantage of predefined layer names and any of their default layer symbology to quickly and easily create well-formatted CAD data.

1. Add a field called 'Layer' to the feature class.
   
   Alternately, use the User Interface (UI) or the Create Field Alias geoprocessing tool to provide a field alias for an existing column with the alias name of 'Layer'.
   
   Another option is to use the field info parameter of the Make Feature Layer geoprocessing tool to temporarily rename a field to 'Layer', which is used to provide the valid CAD layer name values to the Export to CAD tool.
2. Confirm that the feature class contains valid CAD layer name values in the 'Layer' field, and/or populate the 'Layer' field with valid CAD layer name values.
3. Provide the feature class as input to the Export to CAD tool.
4. Optionally, include the corresponding Microstation or AutoCAD seed file that contains the same layer names as those referenced in the 'Layer' field of the input feature class(es). A seed file can contain default layering symbology such as a layer's default color, linestyle, line width, and so forth.
   
   Alternately, specify the CAD layer properties by including the specially named CAD fields in the input feature class(es). By including the specially named CAD fields 'LyrName', 'LyrColor', and so forth, new CAD layers can be created with the specified layer properties. This only works when creating a new CAD file where the referenced layer names do not already exist in the CAD seed file.
   
   Specifying the CAD layer properties is a way to control the output CAD symbology by allowing entities to assume the values of the layer symbol properties without explicitly defining each entity's color, line style or other graphic properties. This works well if all or most of the entities on a CAD layer use the same symbology.
5. Execute the Export to CAD tool with the valid input parameters.