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How To: Define the projection for CAD data for use in ArcMap

Summary

Computer Aided Design (CAD) files can be brought into ArcGIS and made to overlay other data in ArcMap by defining the projection (coordinate system).

Instructions provided describe how to define a projection for using CAD data in ArcMap and apply to DWG or DXF files created in AutoCAD and to DGN files created in Microstation.

Procedure

  1. CAD data can be created in a real-world coordinate system, such as State Plane or UTM. This is the spatial reference of the CAD data, and information about the spatial reference should be obtained from the data source. If the CAD data was created in a real-world coordinate system and the data source provides the necessary parameters, go to Step 2.

    • For help identifying the coordinate system used to create the CAD file, if the data source does not have the projection information available, refer to Knowledge Base article 24893, How to identify an unknown projected coordinate system using ArcMap, to identify the projection for the CAD file.

    • Article 29129, How to identify the spatial reference, projection, or coordinate system of data, can help to determine whether the coordinate system is geographic, projected, or local.

  2. Having obtained the spatial reference (projection) parameters for the CAD data, define the projection for the CAD dataset by the following steps:

    A. Go to ArcCatalog and display the Catalog Tree.
    B. Right-click the CAD dataset and click Properties.
    C. Select the Spatial Reference tab and click the Edit button.
    D. In the Spatial Reference Properties dialog box, click Select.
    E. Open the appropriate Coordinate System folders.
    F. From the selections shown, select the projection file that contains the projection parameters given for the CAD dataset.
    G. Click Add.
    H. Click Apply on the Spatial Reference Properties dialog box.
    I. Click 'Save as...'
    J. Navigate to the directory where the CAD file is stored on the computer.
    K. Give the projection file the identical name as the CAD dataset, substituting the extension .prj.


    For example, if the CAD file is named 'Parcels020305.dwg', the projection file will be renamed 'Parcels020305.prj'.

    Warning:

    • The projection file must be saved in the same directory as the CAD file.
    • With the exception of the extension, the projection file name must be identical to the CAD file.
    • The file name is case-sensitive.

  3. If the CAD data was created in a local coordinate system, a custom projection file can be created for the CAD data to align the CAD file with other data in ArcMap. Refer to Knowledge Base article 32939, How to create a custom projection file in ArcMap to align CAD data.
  4. Beginning in ArcGIS Desktop version 9.3, if many CAD files in the same coordinate system are received from the data source, the projection for all the CAD files can be defined with a single projection file using the steps below.

    A. In Windows Explorer, navigate to the installation folder for ArcGIS Desktop, open CoordinateSystems\Projected Coordinate Systems\, and copy the projection file with the correct parameters for the CAD files.

    Note:
    At version 10.1, open ArcMap > View > Data Frame Properties > Coordinate System tab. Browse to the projection definition that applies to the CAD file, right-click it, and click Add to Favorites. A physical copy of the projection file is written to the location of the user profile.

    B. Navigate to the directory where the CAD files are stored on the computer, and paste the projection file into that directory.
    C. Rename the projection file as esri_CAD.prj.

    • The projection is defined for all the CAD files in that directory.
    • This method also defines the projection for any CAD files that have been saved with spaces in the name.

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