The mode Ruler is turned on by pushing the button 
. This mode enables the user to measure different lengths and areas in the displaying pane. The cursor takes the form of a cross: 
and the window “Ruler” is opened (figure 12-8).
Figure 12-8. Window “Ruler”
Clicking the necessary pane points (for example, in the corners of some area feature), it is possible to build a polyline and see the information about separate polyline segments (end coordinates, length, slope angle) and about the polyline in general in the window “Ruler”. It is possible to cancel unsuccessful selection of a vertex performing the operation Rollback from the context menu. When the box Autocomplete is checked, the system builds not a polyline, but a closed polygon and gives data about its area.
If the next polyline vertex should be located in the point with coordinates known in advance, instead of clicking the command Add from the context menu can be performed. The dialog box “Adding vertex” is opened, in which vertex coordinates should be specified.
Building a polyline or a polygon is completed after a double click the last vertex. After that it is possible to build another figure, the previous one disappears from the screen, but its length and area are taken into account in total values until the button Reset is pushed.
The window “Ruler” will be closed after selecting any other mode.
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