Problem of Buffer Zone Construction in GIS

On the basis of program practice concerning several approaches to construct buffer zone for cartographic and GIS data handling. Analysis and comparison between method of angular bisectrix and method of circular arc are analyzed. The former often brings out graphic anomalies which can require further multi-criteria judgement and corresponding correction processing. That would make this method difficult to be used.As the opposite with the method of angular bisectrix a circular arc method for construction of double parallel lines of buffer boundary has been developed. The latter method is based on the enhanced judgements (convex/concave judgement, controllable chord to arc approximation) guaranteeing the width equality to the utmost extent. The core issue is the treatment of circular arc method which is based on the double mathematical models: the geometric model for constructing the double parallel lines and the relation handling model for detecting the islands and overlapping areas. Both islands and overlapping areas have symmetric structure properties: islands of left bound line appears in anticlockwise,but overlapping areas clockwise. For right boundary line the situation is completely opposite. The island polygons should serve as components of final parallel lines or buffer boundaries. At last, scheme of construction buffer zones for tree structure of line objects and complex network configuration is proposed.