This mode permits selecting all features intersecting the specified circle (that is, having common points with it). The system opens an auxiliary window “Selection circle”.
To specify selection circle it is necessary to place the cursor in the center of the circle, push the left mouse button, move the cursor to the boundary of the circle and release the button.
The set selection threshold is used to determine selected features.
Additional possibilities of performing selection and deselection of features are connected with using the keys Ctrl, Alt, Shift.
The button 
of the mode toolbar in map browser window.
Modes of selecting by rectangle, circle, polyline or polygon
Using the keys Ctrl, Alt, Shift when performing selection
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