Suitable and unsuitable plans for georeferencing
Suitable types of plans
Plans similar to the examples below would be suitable for georeferencing.
Example 1
These deed plans are based on the OS Map and there are sufficient features shown on the plans to use as control points to transform the map images to the OS Map, allowing the boundaries and pipe features to be plotted on the cadastral map. Affine Transformation should be possible with this type of deed plan.
Example 2
This plan is based on a prior version of the Ordnance Survey map at 1:10560 scale. There are a sufficient number of boundaries and features from which to relate the deed plan image to the OS map so this plan should be able to be accurately georeferenced.
More than four control points may be required for examples like this to accurately transform the plan.
Example 3
Although this plan is not based on the OS Map, comparison with the OS map shows that the four points numbered on the image and located outside of the subjects are defined on the map and can therefore be used as control points to georeference the subjects.
Example 4
Although this deed plan is based on the County Series map, examination of the deed plan with the OS map shows that there are sufficient intersections of features and commonality between the deed plan image and the OS Map to allow this to be accurately georeferenced.
Unsuitable types of plans
The following types of plans are not suitable for georeferencing for one or more of the following reasons
a) They are not based on the Ordnance Survey Map or County Series Map
b) There are insufficient control points to use to georeference the image
c) The deed plan is too small a scale
For Example 1 and Example 2, it is more efficient and accurate to plot and scale using the Adobe Reader measuring tool. Further guidance on this can be found in the Core Mapping Skills Online Course on Plotting and Scaling.
Example 1
This plan is not based on the OS map, but it does have a scale bar that can be used to enable the plan to be plotted and scaled in Adobe Reader.
Example 2
This plan is not based on the OS Map, but it does have measurements on the boundaries that can be used to enable the plan to be plotted and scaled in Adobe Reader to plot the path hatched black.
Example 3
The deed plan is at far too small a scale for the boundaries to be accurately defined on the cadastral map. The width of the boundary edge is some 100m wide, obscuring the underlying map.