Creation of a polygon based on the boundaries of surrounding contours

This mode is designed for creating a multipolygon formed by the boundaries of polygon contours and linear objects within a specified closed contour, a selected object, or within the map window area around a specified point.

The area for constructing the multipolygon can be selected in one of the following ways:

• By circular mouse movement with the left button pressed or by sequentially selecting contour points;

• By specifying a rectangular fragment with the Shift key pressed;

• By selecting an object on the map after pressing the Spacebar.

With this area selection, only polygon contours and closed linear objects participate in the construction. The construction may result in the formation of a multipolygon. When constructing a multipolygon, area objects (polygons) and closed linear objects that are selected on the map are cut out. If no objects are selected in the map window, all objects intersecting the specified contour are cut out. If the contour degenerates as a result of the cutting, a new object is not created.

If, before starting to draw the contour line or pressing the Spacebar, you press the Ctrl key and left-click the mouse over an area or closed linear object, the contour for which the specified point is interior will be selected as the construction area. If the specified point lies inside several contours, the intersection of all such contours will be constructed.

If, before starting to draw the contour line or pressing the Spacebar, you press the Ctrl key and left-click the mouse over an empty area, a rectangular contour sized 3/4 of the current map window, centered at the selected point, will be selected as the construction area. If several empty areas of the map fall within the specified area, only one object encompassing the selected point will be created.

When the Ctrl key is pressed, the current size of the void construction area will be displayed as a transparent rectangle. To decrease or increase its size, additionally press the Shift key together with "-" or "+".

Decreasing the void construction area is performed when the linear contours necessary for boundary construction do not extend beyond the construction area boundaries or beyond other adjacent polygons (i.e., they do not completely cut through the area).

After positioning the rectangle at the desired size over the void boundary construction area, you must press the left mouse button without releasing the Ctrl key.

When constructing a polygon around a point that falls on existing polygons on the map, the size of the construction area does not matter.