Background

Accurate Network Design and modification, relies on up-to-date Landbase/cadastral information. Maintaining this up-to-date data has been, in the past, a difficult job due to the delay between the “real world” field changes (eg land subdivisions) and the production of a digital representation. This delay is often several months or even years. The Design Loader and Maintenance Tool (DLM Tool) has been developed to produce temporary Landbase information based upon proposed subdivision information. Using this new information, the Network Design could be modified to fit, until the authoritative version is available.

DLM Tool Process

To accurately overlay a subdivision from Smallworld using a DXF data format the following process is required. This process includes loading the DXF files, transforming them to the correct shape for the local coordinate system and fixing this data into place. It is also important to handle changes in the shifting Landbase.

DXF files:

The DLM Tool uses subdivision information provided in DXF form. A standard format for every DXF file needs to be established which defines which layers will be provided and what data is on each layer. The DLM Tool can then be customised to read in each DXF. If a DXF file doesn’t match the specified format, errors can occur.

Transformations:

Because the DLM Tool reads in DXF data from an arbitrary coordinate system, an Affine Transformation is used to shift, rotate and scale the proposed land data into the existing Landbase. A minimum of 3 control points is required to do this.

Control Points:

When placing control points, there is a requirement to have some overlap between the proposed data and the existing Landbase. Without this overlap, it is impossible to transform the DXF file.

Landbase Updates:

When new Landbase updates arrive, the DLM Tool can be triggered to find any that may replace proposed data.