Data Points

What is a Postcode Boundary?

  • 1.  What is a Postcode Boundary?

    Posted 05-19-2019 09:44

    I have had lots of conversations with end users where I realised I needed to go back to basics to help them understand what a postcode boundary really is, and that is location analysts we use them for a different purpose than what they were created for. I decided to out together an overview.

    Postcode boundary data has been a core dataset for GIS and spatial analysis for well over 25 years, providing an enclosed boundary defining the area covered by a single postcode such as a US 5 digit zipcode, a UK postal Sector or an Australian 4 digit postcode.
    The Location analytics and GIS community have found postcodes to be an effective way of aggregating and displaying a variety of data for market analysis, visualization, target marketing and simple geocoding. However we are seeing increasing use of postcode boundaries in new applications which are deployed large scale processing environments with ever larger volumes of data being used to analyse a location. These new applications includes mobile location data analysis, location based marketing and social media advertising, and are deployed in operational environments as apposed to the traditional GIS desktop analysis. At Pitney Bowes we believe it is important to reflect and understand what postcodes are for and how postcode boundaries are built.

    Postcodes are created by postal authorities, such as the Royal Mail in the UK and USPS in the US, to deliver post and are based on the efficient routes for the delivery of physical mail, they are not designed to create well organised, discrete boundaries. Unlike administrative boundaries, there is no official demarcation of postcodes and what the boundary effectively does is define the most likely boundary area.

    • Postal data can be non-geographic, were there is no specific single address associated with the postcode which means that it cannot be spatially referenced
    • PO Boxes that are assigned to a post office point location and therefore do not have an area
    • Large business locations which have their own postcode. This can mean that illogical

    Remember it's about delivering post not creating neat polygons. These characteristics mean a postcode boundary is a representation of the area, you can get better representations of those areas but there is no official demarcation line between different postcodes. 

    Postcodes also change regularly, changes will include new postcodes, postcodes being retired, splitting postcodes, additional addresses associated with a postcode. These changes reflect the real world where there are new developments, areas being demolished, population increase and decrease plus more efficient postal delivery. Therefore the postcode boundaries must be updated regularly to reflect these changes.

    Andy Bell
    Global Data Product Management
    Pitney Bowes Software & Data
    Leeds, UK