In ObjectLand the digitizer is used only in interactive entering and editing map features as an alternative to using of a mouse.
To perform entering of map features using the digitizer the user should perform setting of configuration and calibration of the digitizer adjusting them to a particular map in advance, open a browser window of the corresponding GDB map (or of a theme on the basis of this map, or of some particular layer or feature type of map) and provide approximate correspondence of displayed fragment of the map to the area displayed on the source “paper” map.
The menu command Tools+Digitizer allows turning on and turning off usage of digitizer when editing a map. The digitizer is used only in the modes of interactive editing of a map, to be more exact, in the modes Adding new feature, Edit, and Adding inner boundary. In all other working modes the presence of the digitizer is not noticed.
If the box Do not use digitizer is checked in the dialog box “Digitizer adjustment” (figure 21-1), the command Tools+Digitizer remains disabled. In this case interactive editing of a map can be performed only using a mouse.
It should be kept in mind that when working without the digitizer the mouse cursor takes one of the various forms shown in the subsection “Cursor shapes in the mode Edit ”, when the cursor is located in displaying pane. In any of these forms the cursor will be called editing cursor below. If the digitizer is used, display of two cursors is shown in the map browser window. One of them is an ordinary mouse cursor which can be used as before for performing such actions as selecting commands in the menu, clicking buttons on the toolbar and so on, while the other is editing cursor which is always located in displaying pane. Its position corresponds to the current position of the hardware cursor of the digitizer on the tablet taking into account transformation from its own coordinates of the digitizer into coordinates of GDB map.
Moving of a mouse does not affect the position of the editing cursor. The mouse cursor in the displaying pane does not change its form, and clicks of the left mouse button in displaying pane are not processed at all. Thus, control of interactive editing of features passes from the mouse to the digitizer cursor.
As a rule, there are not less than four buttons on the digitizer cursor, some models have much more buttons. Some application programs permit linking of each button with some command which is performed after clicking this button. In ObjectLand only two different commands correspond to digitizer buttons. One of the buttons (main button) corresponds to the left mouse button in the mode of interactive editing of features. Clicking this button can denote selection of a feature or of its vertex for editing, adding of next vertex when entering a feature, adding a point feature, etc. depending on a concrete situation. Clicking any of the rest buttons of the digitizer is equivalent to a double-click of the mouse button. It is used mainly for completing creation of a line or area feature.
No button of the digitizer can be used in ObjectLand instead of the right mouse button. To open a context menu it is required to click the right mouse button, whether the digitizer is used or not. To select an item in the context menu, the left mouse button is used.
If there is no display of the editing cursor in the editing pane, it can be explained either by incorrect calibration of the digitizer or by the fact that a wrong fragment of the map which is fastened at the tablet of the digitizer is displayed in the pane. To prove this it is necessary to compare coordinates of the editing cursor displayed in the status bar with coordinates of the displayed region which can be obtained in the property sheet of displayed theme on page “Fragment” (see figure 15-1). If coordinates of the editing cursor lie outside displayed fragment, this cursor is not visible.
Using of the digitizer allows rather fast and precise digitalization of the source map. The user moves the digitizer cursor along the source map positioning it on feature vertices precisely using the viewfinder. Every click of the digitizer button causes adding of a feature vertex, coordinates of the map for the vertex being added are calculated on the basis of coordinates of the digitizer cursor at the moment of clicking using transformation coefficients obtained in calibration.
It is possible to use the digitizer by analogy for editing the features created before. All editing procedures are performed exactly in the same way as described in chapter 17 “Adding and editing features” with the exception that moving of the editing cursor and clicks by the left mouse button are performed not using a mouse, but using the digitizer cursor.
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