You can define a spatial reference for CAD datasets in the following two ways:
- Use the CAD Feature Dataset Properties dialog box.
- Use the Define Projection geoprocessing tool.
The CAD Feature Dataset Properties dialog box
Defining a spatial reference with the CAD Feature Dataset Properties dialog box is performed in a Catalog window. This method stores the coordinate system differently depending on the file format and format version. If the CAD dataset is an AutoCAD drawing version 2007 or higher, it embeds the spatial reference in the source file. For all other formats and versions it creates an auxiliary projection (.prj) file.
To open the Spatial Reference Properties dialog box, right-click the CAD dataset in a Catalog window and click Properties. In the CAD Feature Dataset Properties dialog box, click the General tab and click the Edit button.
Select an existing coordinate system
To select an existing coordinate system, click the coordinate system in the list box and click Ok.
Import a coordinate system
To import a coordinate system, click the Add Coordinate System drop-down menu from the menu bar and click Import. Browse to the file and select it, then click Add.
You can import a coordinate system from other CAD datasets or from ArcGIS formats such as shapefiles, rasters, or geodatabase feature classes.
Create a universal projection file
To create a universal projection file, right-click the coordinate system in the list box and click Save As. Name the file esri_cad.prj and save it in the same folder along with the CAD files.
The Define Projection tool
Defining a spatial reference with the Define Projection tool can be performed in a Catalog window or in a geoprocessing model. This method always generates a projection (.prj) file regardless of the CAD file format. It names the projection file to match the drawing file name and saves it in the same folder. For AutoCAD drawings version 2007 or higher, this can effectively override a spatial reference embedded in the source CAD file.
The tool is located in the Data Management > Projections and Transformations toolset.