To Rubbersheet an Image

Note: Use the match feature to get the image as close as possible to the desired result before you begin rubbersheeting.

1. Click Raster menu CorrelateRubbersheet.
2. Select the image to rubbersheet.
   Note: If there is only one image in the current drawing, that image is automatically selected.
3. On the Rubbersheet dialog box, select a method: Triangular or Polynomial.
4. Choose one of the following rubbersheeting methods:
   • Manually add control points by picking directly from the image. Follow steps 5 to 8.
   • Create a grid of destination points to which you can match source points. Follow steps 9 to 15.
   • Import a list of saved control points by clicking Import and choosing the .txt file from the Open dialog box.
     Note: When you click OK, Rubbersheet automatically saves the last control points you enter to a file named LASTRS.txt in your Temp folder.

   The Rubbersheet dialog box displays the exact coordinates of each source point and destination point, and the amount of error (if any).

   Pick control points

5. Click the Add Points.

   The Rubbersheet dialog box disappears and AutoCAD Raster Design toolset prompts you to select the first source point. You must select at least three pairs of source points and destination points.

6. Select the first source point for the first control point on the image.
   Note: You can select points on specific raster entities by using raster snaps.
7. Do one of the following:
   • Specify the destination point to which the source point should be moved.
   • Type a to anchor the selected point where it is.
   • Type u to undo the point and select the point again.
     Note: If you are using AutoCAD Land Desktop, you can substitute COGO points by typing .p, .g, or .n when AutoCAD Raster Design toolset prompts you to enter destination points. For more information, see Snapping to COGO Points.
8. Select at least three more pairs of source and destination points, and then press Enter to return to the Rubbersheet dialog box. Go to step 16.
9. Click Grid Points.

   The Rubbersheet dialog box disappears and the Grid Parameters dialog box appears.

10. In the Points section, choose how many rows and columns of points you want to comprise the grid.

    The total number of points in the grid is displayed at the bottom of the Points section.

11. In the Grid section, enter the X and Y origins of the grid, or click Pick to choose the grid origin directly from the drawing (pressing Enter to return to the Grid Parameters dialog box).
12. In the Cell section, enter the X and Y sizes to determine the distance between columns and rows (respectively), or click Pick to draw a two-point rectangle representing the cell size directly in the drawing (pressing Enter to return to the Grid Parameters dialog box).
13. Click Preview to see a representation of the grid in the drawing (pressing Enter to return to the Grid Parameters dialog box).
14. Click Add Points to match source points to the grid of destination points.

    The Grid Parameters dialog box disappears and AutoCAD Raster Design toolset automatically pans to the first destination point.

    Note: You can select points on specific raster entities by using raster snaps.
15. Do one of the following:
    • Click to enter a corresponding source point for the current destination point.
    • Type a to anchor the selected point where it is.
    • Type s to skip to the next destination point. AutoCAD Raster Design toolset will return to this point when the other destination points have been matched to source points.
    • Type u to undo the point and select the point again.

      AutoCAD Raster Design toolset automatically pans to the next point until all of the destination points have been matched to source points.

16. If you selected Polynomial as the transformation method, and you entered six or more control points, you can adjust the polynomial Degree value.

    This decreases error by increasing the degree to which an image can be transformed in order to match control points.

    Note: It is a good idea to use the lowest possible polynomial degree that will still give you an acceptable result. Higher polynomial degrees result in smaller errors at the control points, but also result in more warping at places where there are no control points.
17. If you want to view a specific point, select that point from the list of control points, and then click Zoom To to view the point in the drawing.
18. If you want to adjust a specific point, select that point from the list of control points, and then click the Repick to enter a new control point.
    Note: Select the Auto Zoom check box if you want AutoCAD to zoom in to the selected control point when you use Repick.
19. If you want to remove a specific control point from the list, select that point from the list of control points, and then click Delete.
20. Click Preview to see the extents of the transformed image before you actually apply the changes. The convex hull of destination points is displayed in red, while the convex hull of source points is shown in blue. Press Enter to return to the Rubbersheet dialog box.
21. Click Export to save your control point set to a .txt file for later use.
    Note: You can import the saved control points to rubbersheet other images, such as superimposed images for the same drawing.
22. Click OK to perform the rubbersheet.

    If you do not get the results you want, use the UNDO command and try again. Use the match feature to get the image as close as possible to the desired result. For more information, see Undoing Edits to an Image.