The AddressBase Plus and AddressBase Premium datasets contain a field named Postal_Address. This field describes “the type of postal delivery that the object is subject to” classifies each property into four categories (M, S, N and C). For more information on the Postal_Address field as it currently stands see the Ordnance Survey specifications for AddressBase Premium or AddressBase Plus.
LocatorHub provides a filter on AddressBase Premium and AddressBase Plus locators which allows you to return locations based on Postally Addressable (M & S) and Not Postally Addressable (N & C). You’d be forgiven for making the assumption that by setting the filter you would see everything that can actually receive mail, and would exclude all things that couldn’t. In fact, it has not been this simple – at least, until now!
Assuming you had the filter set, under the original classifications, a lot of the time you get what you would expect to see, but sometimes you might be surprised by addresses that seem to be missing. The locations most commonly causing confusion were those classified as C. They are most often flats in a converted building which still has a single letter box on the front door. For instance, 56 the High Street was converted and now has 2 flats, 56a and 56b. Until now, the individual flats would not have been returned and many other buildings that could receive mail, like Church Halls, would also not have appeared. The easiest way to think of the original classification system is whether it has it’s own letter box or whether it shares one.
After feedback from and consultation with customers and partners, the Ordnance Survey (OS) have decided to change this classification system to one that better meets customer requirements. In the future the Postal_Address will define “records that are capable of receiving mail” and will be either S (yes it can) or N (no it can’t). The OS are working on making these changes to the data. In the interim, we have added a function to LocatorHub so that when you load your AddressBase Premium or AddressBase Plus data this code can be re-calculated to what it will be once the OS have implemented their changes. If you load your AddressBase data using this option, you will now be able to use the Postally Addressable filter on your locator to correctly filter out addresses which either can or cannot receive mail.
Don't worry if you use the data to find the links between ‘parent’ and ‘child’ addresses (such as 56 the High Street, and the 2 flats within the building); this information is elsewhere in AddressBase data and you wouldn’t use this code for that purpose.