Higher level boundaries have been manufactured from these using a range of indexes and directories. These include Poor Law Unions and Counties, Registration Districts, Administrative Units and Counties, all for England and Wales, and London Registration and Sub Districts. This numerical representation consists of sets of co-ordinate pairs that define polygons which, when used in conjunction with appropriate software, can be used to produce outline or shaded areas in thematic maps of census and other statistics. The co-ordinate pairs correspond to the National Grid. The map below is a straight-forward example of what can be achieved using a combination of digitised boundary data and census statistics.
Software products differ in the digitised boundary data formats that they can handle.
Anyone intending to access the digitised boundaries described here ought to investigate, at an early juncture, which mapping software they wish to use within their own computing environment. This decision should be made prior to accessing the data. In order to gain access it is necessary to register. Intending users should obtain a copy of the registration pack from the technical site representative at their institute. Each licence must also be witnessed.