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How To: Transform the coordinate location of a CAD file

Summary

A CAD world file can be used to transform the coordinate location of CAD drawings. A CAD world file is a simple text file with a '.wld' file extension containing four coordinate pairs, and can be easily created with a text editor.

Procedure

A reference theme is needed that occupies the coordinate space to which you want to transform the CAD layer. This theme should have some features in common with the CAD drawing.

  1. Create a new view and add the CAD drawing.
  2. Find two points in the CAD drawing that can be easily identified in the reference theme. For example, road intersections.
  3. Obtain the input coordinate values for the control points identified in step 2.
    a. Open the view containing the CAD drawing.
    b. Zoom in on one of the points.
    c. Place the cursor over the point.
    d. Write down the coordinates shown in the upper right-hand corner of the ArcView window.
    Hint: If the coordinates change when moving the mouse slightly, zoom in further.
    Note:
    In ArcView, the X coordinate is displayed above the Y coordinate.
  4. Obtain the output coordinate values for the control points identified in step 2.
    a. Open the view containing the reference theme.
    b. Zoom in on the corresponding control point.
    c. Place the cursor over the point.
    d. Write down the coordinates shown in the upper right hand corner of the ArcView window.
  5. Open a text editor, such as Notepad or WordPad.
  6. Type in the coordinates that were just collected; use the following format:
    cad-x,cad-y ref-x,ref-y 
    For example:
    10.23456,118.67901 4350098.23,37234765.45 
    Note:
    A space character goes only between the CAD and Shapefile (reference theme) coordinate pairs, not after the commas. 
    Leave the text editor open.
  7. Open another new view and add the reference theme.
  8. Repeat steps 3 through 6 with the other control point. In step 5, add the line underneath the one just written so it looks like this:
    cad-x,cad-y ref-x,ref-y
    cad x,cad-y ref-x,ref-y 
  9. Save the file with the same name of the CAD drawing and with a .wld extension. For example, caddrawing.wld.
    Note:
    When saving the file, be sure the file type is set to 'All Files' or '*.*'.  If not, the text editor will append a .txt extension onto the file and the transformation will not work. Placing quotes around the filename also prevents the text editor from adding an extension to it. 
  10. Open a new view and add both the CAD drawing and the reference theme.
  11. Open the Theme Properties for the CAD drawing and click the Drawing icon.
  12. Click the radio button for World File in the Transformation box.
  13. Navigate to the directory where the .wld file is saved and select it.
  14. Click OK on the Theme Properties dialog box and click the 'Zoom to Full Extent' button on the view. The CAD file should now overlay the shapefile.

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