Sino-Korea Chongqing GIS Research Center;
College of Computer Science;
Chongqing University of Posts and Telecommunications;
Chongqing 400065;
P. R. China;
Department of Computer Science and Information Engineering;
Inha University;
Incheon 402-751;
Korea;
Department of Computer Education;
Seowon University;
Chungbuk 361-742;
Korea;