Strategies and issues with improving positional accuracy of the Queensland Digital Cadastral Database
The Queensland Digital Cadastral Database (DCDB) was developed by manually digitising the best available cadastral maps. In 1992, the digital capture was completed at the agreed standard. The outcome was a seamless database of the cadastral network compiled to a range of accuracy ratings. Positional accuracy was derived as a factor of the map scale and the precision of the digitising. Consequently, the positional accuracy of the DCDB throughout Queensland varies from 0.1 metre to 250 metres.
Data in the DCDB consists of two parts. A spatial component is used to depict the position and boundaries of parcels and the attribute information contains details about each parcel. The spatial component of the parcel is adjusted while the unchanged attribute data moves with the adjusted parcel. The integrity of the database is maintained.
Today, there is an increasing need for improving the spatial component's accuracy. The DCDB has evolved to become the essential point-of-truth data source which underpins all land information systems used by state and local governments as well as private businesses.
NRMW currently utilises two schemes for improving spatial data accuracy. They are:
• NRMW encourages local governments to embark on upgrade projects as a cooperative under individual license agreements. This upgrade process may include full re-entry of bearing and distance from survey plans or employ some form of numerical or graphical adjustment.
• The Graphical Relativity Project was established to progressively improve the positional accuracy of the DCDB in the rural and remote areas of the state. This project will meet internal requirements for natural resource management needs. Currently these areas have an accuracy indicator ranging from 63 metres to 251 metres. The upgrade is achieved by comparison of existing DCDB with current orthorectified satellite imagery or, where available, 1:40,000 orthophoto images.