This page provides an overview of the cadastral process commonly described as Fit to Fabric. This is a common workflow performed by custodians when they wish to take on board new data, but do not wish (at the time of processing) to materially distort the current cadastral parcel base. In other words, accept and process the new data into the system, but do not cause change in in the fabric beyond the internal extent of the scope of the subject survey works (subdivision or consolidation). This document focuses specifically on the take-on and processing of a sample ESRI CEXML file.
It should be noted that all data that is contained within any processed CEXML file is decomposed into its many component parts and stored to database tables for later use in cadastral improvement and upgrade works.
Whilst our standard solution is designed to ingest the ICSM ePlan LandXML based standard files, we will support whatever (structured data) file format our users require. In this instance, Northern Territories supplied ESRI standard CEXML1 files for the purposes of this case study, we were able to quickly enhance our translators to support this transfer format as well .
1Note: no accompanying xsd file was supplied, current translation is based solely upon XML elements found within the range of the sample files provided (readily extensible).
The following outlines a specific subset of processes that we have applied to an example CEXML survey plan.The data used is:
The Fit to Fabric process represents common practice amongst custodians trying to avoid the supply of continuously changing update data out to client organisations. This is to avoid the situation or creating continuous and ongoing downstream data re-integration in the supply chain. It is a much preferred practice that custodians Upgrade larger blocks of cadastral data on a programmed basis; and then supply that new data to clients along with the relevant shift-vector data set (to facilitate asset re-alignment).
Working with the original parcel fabric, the following serves to demonstrate load, shred, auto locate and process the supplied CEXML file into the parent fabric identified by 'A'
Same area showing existing point data. Curved boundaries are represented by arc segments (which is the typical case in most current GIS based cadastres)
The CEXML file has been read into the system and shredded. This means that the file has been broken down into its many constituent parts and stored to database tables. At this point in time, the CEXML plan is rendered as lines and polygons (in orange) overlaying the base cadastre.
Zooming in to the top North Western corner, the area framed in blue in the above diagram, shows a growing discrepancy between the CEXML location for the curved western boundary and that of the existing cadastre.
Zooming in even further, to the blue rectangle above, clearly shows a misalignment between the two boundaries.
The next action is to invoke a REST call to generate shift vectors between the original cadastral parcels and the newly onboarded CEXML survey data. These are generated automatically and usually results in a greater than 95% match against the existing Cadastre.
At this point in the processing, we would usually perform a brief eyeballing of the shift vectors to ensure that there are no obviously erroneous ones (and would delete those). In addition, whilst doing this, if we develop a sense that a little bit of assistance might be needed to facilitate the next stage of processing, we might also choose to add additional shift vectors via manual snapping.
We then perform an adjustment on the data (as limited as it might be at this point) in order to obtain the best all round shape on the newly submitted CEXML parcels. Three types of adjustment are facilitated:
Once we have performed an adjustment, we then invoke our conflation routines. These routines make use of the shift vectors to bring the main cadastral corners (nodes) into coincidence. Further calculations then follow to re-incorporate any boundaries with arc parameters and to insert any newly created node points along the arc.
The resulting (downgraded) plan, shown in purple, can be seen to have needed to stretch the new plan features to match the original Western boundary.
Image showing the vertices for arcs in the original base Cadastre. This is in the pre-reconcile phase between newly computed amd reconciliation actions.
Showing the vertices of both the original and the CEXML plan features, as loaded. Clearly seen, is the shortfall in the new plan image data relative to the existing cadastre.
On the Western boundary (along the road frontage) the original cadastral vertices have now been adopted from the original cadastre. Only the two new parcel nodes (circled) are added at the point(s) where the boundaries intersect.
The original cadastral data without the strata title boundaries shown. It is a common occurence across the jurisdictions that strata infill is not available in digital form.
Showing the new cadastral boundaries fitted automatically to the underlying cadastral fabric. All that remains from here is for the new configuration to be reconciled back to the authoritative cadastral database.
This case study demonstrates an automated process to:
Once sufficient dimensioned plans have been inserted into an area, the myCadastre solution can be used to simply and efficiently improve the spatial alignment of the cadastral fabric by running either an 'iterative best guess' or a rigorous 'least squares adjustment' based on the stored plan dimensions and connections to survey control. This would be a simple addition to this case study when more CEXML files for the Driver suburb are available.
Additionally, if digital plans are not readily available (either new or current Cadastral plans), the myCadastre cCogo Capture tool can be used to efficiently capture all required plans. Being web based the cCogo can be provided to any stakeholder with an interest in improving the spatial accuracy in an area.