Chongqing Institute of Technology;
Chongqing 400050;
P. R. China;
Sino-Korea Chongqing GIS Research Center;
Chongqing University of Posts and Telecommunications;
Chongqing 400065;
P. R. China;
Dept. of Computer Science and Engineering;
Inha University;
Inchon 402 751;
Korea;