Why Calibrate the Tablet?

When you want to digitize points, polylines, or polygons from a paper document, you must first calibrate the digitizing tablet using the Didger Tablet Calibration Wizard. Digitizing tablets have an internal coordinate system that is not related to the coordinate system of your document. Tablet calibration is how Didger determines the relationship between your paper document's coordinate system and the coordinate system of the tablet.


Before you calibrate the tablet, you must select between three and 256 calibration points on your paper document, and determine the document XY coordinates for these calibration points. When you place the document on the digitizing tablet, the document calibration points are placed over specific tablet locations. The Tablet Calibration Wizard asks you to enter the document coordinates for your calibration points and then click each calibration point. This way, Didger knows where these document calibration points lie in relation to the tablet coordinates, and can then convert all subsequently digitized object coordinates to document coordinates for use in Didger.


Once you have calibrated the digitizing tablet, you are ready to digitize objects from your paper document. This is the actual transfer of data from your paper document to the computer. During this procedure, you transfer the document location of objects as well as names or data associated with each object. A Didger project can contain any number and combination of objects.



See Also

Didger Object Types - Points, Polylines, and Polygons

Introduction to Digitizing  

Didger Project .PJT Files