It is necessary to perform a calibration of the digitizing device before each digitization. The calibration consists of determining identical points which will be used to transform the graphic coordinates into real ones. The process of entering the identical points is the same as when transforming the coordinates :
Select the required type of transformation. For graphic templates, the affine transformation, which has two different scales in the directions X and Y, is suitable (unlike the similarity transformation which has the same distortion scale in all directions). For the similarity transformation, at least two identical points are necessary, for the affine transformation three. For reliable results of the digitization to have always at least 1 - 2 extra identical points is suitable.
Enter the real coordinates of the identical points in the boxes X and Y, preferably by mouse dragging from the coordinate list.
Read the graphic coordinates on the digitizing device. These coordinates will display in the boxes x' and y'.
Add a point to the identical point list by pressing the button (Add).
You can turn the individual points on the identical points list on /off using the check box at the beginning of each line. If you want to remove the point form the list completely, press the button (Remove)
You can view and save the calibration report after pressing the button (Report).
If you want to start the transformation of a new template, press the button (New transformation).