Drafting on the background of scanned images can be made more convenient and productive with help of SuperEdit ’s selective Raster snap function. Snapping to raster features may be enabled permanently or transparently called from within SuperEdit commands.

Open the office.tif image as described previously. Choose the Options - Configuration option and select the Snap tab. Check the Snap to raster active option and the following Snap modes : Intersection of raster lines and Corner of raster line . Increase Pickbox size to 20, or so. Make sure that the Magnifying Glass options Verify every snap trial and Keep on display are checked. Click the OK button. The Raster snap pickbox will be added to the cursor, indicating that the continuous snap to raster mode is active.

Use the Document - Add New Vector option to add empty vector.tvd drawing and to enable the Vector toolbar. Use Segment button to draw the segment overlapping a vertical dimension line labeled 13.28 . Place the pickbox around one end tick of that vertical dimension line and enter the point by the left mouse click. Magnifying Glass window pops up to show the result of snap to the intersection point. If the position of the snapping cross is correct, accept it by clicking the right mouse button. Otherwise, place the cursor correctly inside the Magnifying Glass window and click the left mouse button. Accept the adjusted position by right click.

Repeat the same action for the other end of the dimension line.

Then use the DWM Properties... option. On Measurement tab of Segment Properties dialog read the length of the segment.

The measured length is 14362.4562 (mm), quite different from the 13.28 (m). You will get much better result when using office4.tif that you may have created doing the resizing or matching exercise described in sections below.

The usability of various snap modes depends heavily on the features of background raster images. It is recommended to use the Magnifying Glass to verify snap results visually and to correct it manually, whenever the automatic snap result is not satisfying.