1. Professor, Western Australian Centre for Geodesy, Curtin Univ. of Technology, G.P.O. Box U1987, Perth 6845, Australia (corresponding author).
2. Senior Physics Engineer, Raytheon ITSS, 1616 McCormick Drive, Upper Marlboro, MD 20774.
3. Lecturer, Western Australian Centre for Geodesy, Curtin Univ. of Technology, G.P.O. Box U1987, Perth 6845, Australia.
4. ARC Research Fellow, Western Australian Centre for Geodesy, Curtin Univ. of Technology, G.P.O. Box U1987, Perth 6845, Australia.