Improved Accuracy of Area Objects in a Geographic Information System Based on Helmert’s Variance Component Estimation Method
Publication: Journal of Surveying Engineering
Volume 135, Issue 1
Abstract
Helmert’s variance component estimation method based on a least-squares adjustment of condition equations is presented, in which the registered area and the coordinates of a cadastral parcel are assumed to be different and independent types of observations with errors in the cadastral parcel area adjustment. The Helmert method is employed for the estimation of variance components of these two types of observations, thus providing a determination of accurate weights between them. At the same time, inconsistencies between the registered and digitized areas of the parcels are adjusted through a least-squares adjustment. The mathematical models for adjusting the boundaries of the parcel areas are derived, incorporating both the area conditions and geometric conditions. An empirical test is conducted and the results are compared to those obtained from the conventional method, assuming that the digitized coordinates are treated as observations while the registered parcel areas are not. The analysis of the results demonstrates that the least-squares adjustment, when based on Helmert’s variance component estimates, refinds the weights of the observations more accurately, improves the accuracy of the adjusted coordinates in parcel digitization, and resolves the inconsistencies between the registered areas and digitized areas of the parcels more rigorously.
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Acknowledgments
The writers thank the anonymous reviewers very much for the detailed and constructive comments, and clarifying this manuscript. The work described in this paper was substantially supported by the National Natural Science Foundation of China (Project No. NNSFC40771174), Program for New Century Excellent Talents in Universities (Project No. UNSPECIFIEDNCET-06-0381), Foundation of Shanghai Dawn Scholarship and Rising-star Program (Project Nos. UNSPECIFIED07SG24 and UNSPECIFIED08QH14022) and grants from the Doctoral Program of Higher Education of China (Project No. UNSPECIFIED20070247046).
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Published In
Journal of Surveying Engineering
Volume 135 • Issue 1 • February 2009
Pages: 19 - 26
Copyright
© 2009 ASCE.
History
Received: Aug 2, 2007
Accepted: Jul 23, 2008
Published online: Feb 1, 2009
Published in print: Feb 2009
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