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The point of truth for property boundaries is the survey plan. You can purchase buy a copy of a survey plan through the Titles Qld online title and image searches page. The cadastral data set is the point of truth for the graphical representation of property boundaries. It was created in 1982 by digitising existing cadastral maps at a variety of scales and accuracies and in the case of Brisbane, this was 1:2500 mapping to which a generic positional accuracy of +/- 1.5m was assigned to the data. In some cases, the data is better than this, and in some cases worse than this. The department has been progressively upgrading data over Queensland to improve the position accuracy, so that the worst positional accuracy in Qld is currently +/-63 metres out west. You can find the parcel boundary accuracy statement in the land parcel attributes within the data.
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