Building the government infrastructure for land record and land parcels involves the creation of a survey database of field measurement, geodetic survey control, and the surveyors’ boundary determinations. The cadastral dataset includes parcels, boundary lines, parcel corners, and control points. With all measurements there are issues of accuracy, but with the least squares method the degree of uncertainty is recorded for incremental accuracy update.

A cadastral fabric is compiled from all the relevant survey and plan data. As the data is entered into the database the accuracy of each element is measured. With the least squares method, adjustments are made to compute the parcel corner points, and these adjustments are recorded for subsequent reference.

Least squares adjustment compares all the lines in the original measurements, and gives them a weighting that are based on the age and accuracy of the survey. Usually there are reasonably small errors in accuracy that are recorded for incremental adjustments in subsequent surveys. If major differences in measurement exist, then there is the need to revisit the site to isolate and address the discrepancies.

ESRI introduced the least square adjustment feature within their ArcGIS Survey Analyst extension in the 9.3 release. This Parcel Editor capability will be offered as a free toolbar in ArcGIS Desktop 10 that is scheduled for release later this year. See this page for more details.

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