1. Ph.D. Student, Grad. Dept. of Industrial and Systems Engineering, Virginia Polytechnic Institute and State Univ., Blacksburg, VA 24061-0118.
2. Dept. of Geography and Resource Management, The Chinese Univ. of Hong Kong, Shatin, N.T., Hong Kong (corresponding author).
3. System Engineer, GIS Research Center, Feng Chia Univ., 100 Wenhwa Rd., Taichung 407, Taiwan.