C. Rizos, T.S. Yan
School of Surveying & Spatial Information Systems, University of New South Wales, Sydney, NSW 2052, Australia
e-mail:  Tel: + 61 2 9385 4189; Fax: +61 2 9313 7493

D.A. Kinlyside
Land and Property Information, Department of Lands, Bathurst, NSW 2795, Australia
e-mail:  Tel: +61 2 6332 8372; Fax: +61 2 6332 8479

_{Received: 15 Nov 2004 / Accepted: 3 Feb 2005}