1. Student, Nagaoka Univ. of Technology, Kamitomioka-cho, Nagaoka City, Niigata Prefecture, Japan; and Manager, Surveying Instrument Division, Topcon Corp., 75-1, Hasunuma-cho, Itabishi City, Tokyo 174-8580, Japan.
2. Professor, Dept. of Civil and Environmental Engineering, Nagaoka Univ. of Technology, Kamitomioka-cho, Nagaoka City, Niigata Prefecture, Japan.