A digitizer is a device for entering graphic data. Transferring of maps from a paper medium to an electronic form is one of the most important functions of digitizers. This transfer is also called digitizing of maps.
A digitizer consists of a tablet working field of which serves for locating source cartographical material and a cursor which serves for selecting points in the working field of the tablet. Digitizer cursor is a device similar to a mouse but differing from it in an outward appearance in the presence of a viewfinder (sight). The viewfinder is supplied with a lens element to provide more accuracy in positioning in selected point of the map.
An important difference of a digitizer from a mouse is that it sends coordinates of the current position of the cursor on the tablet to computer, while a mouse transfers only the data about direction and value of shift from the previous position.
When entering data using a digitizer is performed, digitizer cursor is moved through the working field of the tablet on which the source map is located and coordinates of vertices of map features are fixed in required points by pushing digitizer buttons.
Before using the digitizer for entering and editing features, the user should perform its adjustment. For this purpose it is necessary to open a map browser window (for any map or theme of GDB) and perform the menu command Tools+Digitizer Adjustment. A dialog box “Digitizer adjustment” shown at figure 21-1 will be opened.
Figure 21-1. Dialog box “Digitizer adjustment”
Adjustment of a digitizer includes two different procedures: configuring and calibration of digitizer.
At first configuring of the digitizer should be performed. Its essence is in specifying basic parameters of connection used when receiving data from the digitizer. Configuring is performed once when some particular model of digitizer is used for the first time.
Calibration of digitizer should be performed each time before beginning to work with a new sheet of the source map fixed at the tablet of the digitizer.
 |  |
