Building a Transformation Grid
These tools allow you to build a transformation grid between two parcel networks.
For example if you have a digitised DCDB set of parcels and you also have a
cadastral parcel network of the same parcels.
You can build a set of Shift Vectors to transform anciliary data from the DCDB(Shift layer) co-ord system to
the 'cadastral'(Reference layer) co-ord system.
Shift Vector - This links two two points, one on the 'Shift' layer and one on the 'Reference' layer.
A set of these shift vectors can be written to a file in a startdard format to allow data sets to be Transformed or
shifted according to the shifts at each vector.
The process has three phases:
1. Compute Shift Vectors - This automatically matches parcels of the same name and shape and
creates shift vectors between the same points on each network.
2. Edit Shift Vectors - Manually add, edit or delete vectors as required
3. Write Shift Vectors to File - Write the vectors to one of several standard shift file formats
including FME format, ESRI format etc.
Compute Shift Vectors
Use the menu option Points/Compute Shift Vectors and enter the reference layer and the shift layer.
The program will match common points, compute the error vector between them and draw a
contour map of the displacements.
The search routine for common points starts by matching parcels by name, then by matching the points within the matched
parcels. A “robust estimator” technique is used to select or reject points according to the shape differences between the
two matched parcels. The rejection criteria (the rejection factor) can be changed to allow for different types of data.
Reference Parcels Layer
Set this to the layer containing the Reference strings.
These are the strings in the correct position and the correct shape).
Shift Parcels Layer
Select the Layer for the parcels to be shifted
Rejection Factor
When two parcels are matched, points outside this tolerance (mtres) are rejected
Max Search Distance
Used when matching points, points outside this search distance are not matched
Compute Shift Vectors
Edit Shift Vectors
Shift Vector Settings
Read Shift Vectors file
Write Shift Vectors file
Write Shift Vectors to an FME format file
Write Shift Vectors to an ESRI format file