The increasing availability of GPS and lower cost aerial (ortho) photography has highlighted the inaccuracies of the old cadastre and with that, the infrasture that has been overlaid on it.

This has implications for safety (Dial before you Dig), efficiency and the ability to share data between organisations to saves duplicating time and money collecting and maintaining it.

The inaccuracy in the Cadastral Layer effectively prevents accurate GPS located features from being used directly in large-scale maps.

The GIS and Surveying communities must either downgrade their GPS coordinates to fit the existing cadastre and related data, or improve their overall accuracy. They have decided to do the latter.

The problem is then that if the cadastral theme is improved the utility (and other) themes are then in the wrong location relative to the cadastral theme. To fix this, all themes must be moved to fit the new cadastral theme, but this is difficult logistically as many of these themes are maintained by separate organizations. The Spatial Adjustment Engine offers the GIS community the first real tool to manage the ongoing upgrade of spatial data.