The mode Edit is provided with a possibility to transform selected area feature into a line feature of one of the types displayed in the present theme. If the feature has inner boundaries, each of its boundaries will be transformed into a separate line feature.
To perform the transformation it is required to execute the command of the context menu Transform+Polygon to polyline. A dialog box “Changing feature type” shown at the figure 18-10 will be opened.
Figure 18-10. Dialog box “Changing feature type”
In the pane Layers all map layers which make part of the browsed theme are enumerated. The pane Feature types contains the line feature types which are a part of selected layer.
After selecting the layer and feature type and pushing the button OK, the dialog box shown at figure 18-11 will be opened.
Figure 18-11. Dialog box “Transforming polygon to polyline”
The user can determine whether it is necessary to remove the source area feature when creating a line feature (the checkbox Remove source feature) or retain the source feature. Transformation with retaining the source feature allows creating a separate line feature which coincides with the outside boundary of the area feature. Besides, the checkbox Complete boundary permits indicating if the obtained line feature should be a closed or open-ended polyline. If this box is cleared, when transforming boundaries of an area feature the edge which connects the last vertex with the first vertex from the ones built when entering this boundary will be excluded from the boundary. It concerns both the outside boundary as well as the inner boundaries of the feature.
If the area feature being transformed has inner boundaries, each of the boundaries will be transformed into a separate line feature.
A reverse operation, that is, transformation of a line feature to an area one, is possible as well. To perform this operation one should select a line feature in the mode Edit and execute the command of the context menu Transform+Polyline to Polygon. A dialog box “Changing feature type” will be opened. It contains area types of all map layers which make part of the browsed theme. After selecting the type and pushing the button OK, the dialog box shown at figure 18-12 will be opened.
Figure 18-12. Dialog box “Transforming polyline to polygon”
The checkbox in this dialog permits indicating whether it is required to remove the source line feature after transformation.
If an incorrect area feature is created as a result of the transformation (for example, if the source line had self-intersections), a message informing the user about it similar to the one shown at figure 18-13 is displayed.
Figure 18-13. Message about incorrectness of feature
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