11.2.1
An ESU ID must be nationally unique, and persistent (that is, it does not change with changes in the information recorded about the ESU).
11.2.2
Where possible ESU Coordinate Records must be captured using the latest version of Ordnance Survey MasterMap® Topography Layer mapping data, although other mapping products, including paper maps can be used as reference or investigation material. It should be noted that in low population rural areas the specification of mapping data may not always accurately reflect the layout of the carriageway and verges in these areas.
11.2.3
ESU Records must be digitised consistently in the same direction for the entire length of the Street. This should usually be undertaken in the direction of the property numbering scheme for the Street.