Postcodes

Postcodes are stored in Code-Point as alphanumerical values with a maximum length of eight characters (the number of characters in a postcode can vary from six to eight). A postcode contains two parts:

• The outcode (also called outward code): The first two to four characters of the postcode, constituting the postcode area and the postcode district. It is the part of the postcode that enables mail to be sent from the accepting office to the correct area for delivery.

• The incode (also called inward code): The last three characters of the postcode, constituting the postcode sector and the postcode unit. It is used to sort mail at the local delivery office.

For example:

When used in an address, the incode is always separated from the outcode by a single space e.g NW6 4DP. The single space counts as a character.

The following table provides a list of the valid formats of postcodes. In the first two columns, an A indicates an alphabetic character, while an N indicates a numeric character. The last column shows how many characters each example postcode contains.

Postcode position

Each postcode unit will be allocated a National Grid reference of a point that falls within the notional extent of the postcode unit, given as an Easting and Northing. This point is the co-ordinate of the nearest delivery point to the calculated mean position of the delivery points in the postcode unit. These coordinates are provided to a resolution of 1 metre.

Where several postcode units apply to one surveyed position (for example, a block of flats or offices), there is an identical location for each. However, there may be instances where the location is imprecise or approximate, due to the manual allocation by Royal Mail of a postcode outside the recognised geographical extent of that postcode. There may also be a small number of instances where coordinates cannot be allocated.

The accuracy of each postcode unit coordinate pair is defined by the Positional Quality indicator (PQI), which provides a quality statement for the position of that Code-Point record. There are seven PQI values for the positional quality. A lower positional quality indicator will be allocated to postcode units awaiting a surveyed position, or which relate to addresses that do not have a surveyed position. Full details of the PQI can be found in the technical specification.

Coordinate reference systems

The coordinates for postcodes in Great Britain (England, Wales, and Scotland) are provided in British National Grid (BNG). BNG uses the OSGB36 (EPSG 27700) geodetic datum and a single Transverse Mercator projection for the whole of Great Britain. Positions on this projection are described using Easting and Northing coordinates in units of metres. The BNG is a horizontal spatial reference system only; it does not specify a vertical (height) reference system.

The coordinates for postcodes in Northern Ireland (BT postcodes) are provided in the Irish National Grid. When loading the BT postcodes into a GIS, you should select the Irish Grid (EPSG: 29902) for the correct projection. If you do not apply the Irish projection, the BT centroid points will not be correctly positioned. For additional information relating to the Irish Grid Reference System, see the Irish Grid reference document here (PDF download).

Available formats

Code-Point is available in the following formats:

• Comma-separated values (CSV)

• GeoPackage (GPKG)

Supply mechanism

Code-Point is only available as national cover of Great Britain and Northern Ireland. The product is supplied in two formats (CSV and GeoPackage) as an online download from the OS Data Hub. Alternatively, you can request a DVD of the product in CSV format from OS Orders.

The product is provided as a complete resupply. Any postcode that is deleted between supplies will not be included.

Product update schedule

Code-Point is supplied to customers quarterly (in February, May, August, and November), incorporating updates from georeferenced Royal Mail Postcode Address File (PAF) and GridLink. GridLink is a joint consortium dataset that provides geospatially referenced postcode data, consisting of UK postcodes, administration areas and health authority codes. The GridLink Consortium comprises Royal Mail, Ordnance Survey, the Office for National Statistics (ONS), Land & Property Services (LPS), and National Records of Scotland (NRS). Each consortium member supplies component data to create the GridLink dataset.

Administrative and health authority codes are allocated to postcodes using a point in polygon comparison against Boundary-Line data.

Coverage and file sizes

Code-Point covers postcodes for Great Britain and Northern Ireland. Postcodes are divided into postcode areas and supplied as 121 files.

The approximate file sizes of the respective data formats are as follows:

• CSV: 198MB

• GeoPackage: 290MB

The header file for CSV can be downloaded from theCode-Point Product Support page on the OS website.

Code-Point data structure

CSV

There are two folders in the root directory: Doc and Data. The Doc folder contains the following files:

• CD_INFO.TXT: Note about the data on this DVD

• Codelist.xls: Lookup table of GSS Codes

• NHS_Codelist.xls: Lookup table of Health GSS Codes

• metadata.txt: Number of postcode units in each postcode area

• Readfirst.txt: Summary of copyright, licence, and data format information

• DISCCARE.TXT: Contains information on the care of DVDs The Data folder contains the following sub-folder:

• CSV: 121 Postcode area files in CSV format

GeoPackage

There are two folders in the root directory: Doc and Data. The Doc folder contains the following files:

• Codelist.xlsx: Lookup table of GSS Codes

• NHS_Codelist.xls: Lookup table of Health GSS Codes

• metadata.txt: Number of postcode units in each postcode area

• Readfirst.txt: Summary of copyright, licence, and data format information The Data folder contains the following file:

• UK_CODEPOINT.gpkg: One postcode area file in GeoPackage format

Code-Point locates over 1.7 million postcode units for Great Britain and Northern Ireland, each having a notional geographical location. Postcodes are an alphanumeric abbreviated form of an address. Postcode units are unique references and identify an average of 15 addresses. In some cases, where an address receives a substantial amount of mail, a postcode will apply to only one address and is defined as a large-user postcode. The maximum number of addresses in a postcode is 100.

Key product features

With each coordinated point, the Code-Point product provides:

• Information about the number and type of postal delivery points in the postcode, including the split between domestic and non-domestic delivery points per postcode unit.

• A positional quality indicator, which indicates the quality of the data underlying the Code-Point location coordinate.

• The country indicator (either England, Scotland, Wales, or Northern Ireland).

• The postcode type (either a large-user postcode or a small-user postcode).

• The National Health Service region and area codes.

• The local government county, district, and ward codes.

Product applications

Code-Point can be used to display and analyse any data collected at the postcode level. This has led to the product being widely used in a variety of applications, including the following:

• Site location

• Enabling web searches

• Market analysis and profiling

• Health and epidemiology

• Resource allocation

• End-to-end journey route planning

• Socio-economic profiling

• Sales targeting