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Code-Point Open is available in the following formats:
Comma-separated values (CSV)
GeoPackage (GPKG)
Code-Point Open is only available as national cover of Great Britain. The product is supplied in two formats (CSV and GeoPackage) as an online download from the OS Data Hub.
The product is provided as a complete resupply. Any postcode that is deleted between supplies will not be included.
Code-Point Open 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.
Code-Point Open covers postcodes for Great Britain.
The approximate file sizes of the respective data formats are as follows:
CSV: 153MB
GeoPackage: 257MB
The Code-Point Open CSV format contains two folders in the root directory: Doc and Data The Doc folder contains the following files:
Codelist.xlsx – Lookup table of Government Statistical Service (GSS) codes.
Code-Point_Open_Column_Headers.csv – Description of column headers.
licence.txt – Important licence information.
metadata.txt – Number of postcode units in each postcode area.
NHS_Codelist.xls – Lookup table of health GSS codes.
readme.txt – Summary of supplied data.
The Data folder contains the following sub-folder:
CSV – 120 postcode area files in CSV format.
The Code-Point Open GeoPackage format contains the following text file in the root directory:
Readme.txt – Summary of supplied data And two folders: Doc and Data
The Doc folder contains the following files:
Codelist.xlsx – Lookup table of GSS codes.
Code-Point_Open_Column_Headers.csv – Description of column headers.
Licence.txt – Important licence information.
Metadata.txt – Number of postcode units in each postcode area.
NHS_Codelist.xls – Lookup table of health GSS codes The Data folder contains the following file:
Codepo_gb.gpkg – One postcode area file in GeoPackage format.
This technical specification provides detailed technical information about Code-Point Open. It is targeted at technical users and software developers.
Code-Point Open locates over 1.7 million postcode units for Great Britain, 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.
This getting started guide focusses on using the product in comma-separated values (CSV) format.
Code-Point Open is a data product and does not include software for analysis but can be used with a variety of programs. Code-Point Open can be loaded into a GIS (geographical information system) for display and analysis of the data. Consult your GIS documentation to establish actual system requirements.
Code-Point Open is only available as national cover of Great Britain. The product is supplied in two formats (CSV and GeoPackage) as an online download from the OS Data Hub.
Updates are supplied quarterly (February, May, August and November) and provided as a complete resupply. Any postcode that is deleted between supplies will not be included.
Code-Point Open covers postcodes for Great Britain. In CSV format, postcodes are divided into postcode areas and supplied as 120 files. GeoPackage format is a self-contained database.
The approximate file sizes of the respective data formats are as follows:
CSV: 153MB
GeoPackage: 257MB
The Code-Point Open CSV format contains two folders in the root directory: Doc and Data The Doc folder contains the following files:
Codelist.xlsx – Lookup table of Government Statistical Service (GSS) codes.
Code-Point_Open_Column_Headers.csv – Description of column headers.
licence.txt – Important licence information.
metadata.txt – Number of postcode units in each postcode area.
NHS_Codelist.xls – Lookup table of health GSS codes.
readme.txt – Summary of supplied data.
The Data folder contains the following sub-folder:
CSV – 120 postcode area files in CSV format.
The Code-Point Open GeoPackage format contains the following text file in the root directory:
Readme.txt – Summary of supplied data And two folders: Doc and Data.
The Doc folder contains the following files:
Codelist.xlsx – Lookup table of GSS codes.
Code-Point_Open_Column_Headers.csv – Description of column headers.
Licence.txt – Important licence information.
Metadata.txt – Number of postcode units in each postcode area.
NHS_Codelist.xls – Lookup table of health GSS codes The Data folder contains the following file:
Codepo_gb.gpkg – One postcode area file in GeoPackage format.
The structure of Code-Point Open supplied in CSV is described in the product's Technical Specification.
The structure of Code-Point Open supplied in GeoPackage is described in the product's Technical Specification.
As Code-Point Open data is supplied in separate .csv files by two-digit grid references, the files will require some processing in order to proceed.
The Great Britain .csv files should be combined with the Code-Point_Open_Column_Headers.csv. To do this:
Before processing the data, create the following folder:
Great Britain
Then, copy all the .csv files from the CSV folder for Great Britain into this folder (120 in total).
Add the Code-Point_Open_Column_Headers.csv (located in the Doc folder) into the Great Britain folder and prefix the name with: aa_
The following is an example of one way to combine all the individual .csv files into a single file by using a .bat batch file.
The .csv file that is created comes to approximately 150MB, and 1.7 million records. If this is opened in Microsoft Excel, only the first million records can be seen as the software cannot display more than this number of records.
To use the batch function:
Copy the following text and paste it into a new Notepad document: copy *.csv outputfile.csv
Save the Notepad document with the file extension .bat (for example, combine_csv.bat) in the Great Britain folder containing the 120 Great Britain .csv files.
Close the .bat file and navigate to the Great Britain folder, where it was saved. Double-click on the .bat file and an MS-DOS window will appear. Once the process is complete, the MS-DOS screen will close automatically.
A new CSV file with the name outputfile.csv has now been created within the Great Britain folder. All the .csv files apart from outputfile.csv can now be deleted as they have all been copied into the one ouputfile.csv.
The outputfile.csv will have two column headers at rows 1 and 2 – an abbreviated version and a full version.
Open the .csv file in a text editor (not Excel) and delete the column header that you don’t want to use, ensuring that any resulting empty row is closed.
You will now have an output file ready for uploading into geospatial software (such as QGIS).
Glossary term | Definition |
---|---|
An open dataset of all the current postcode units in Great Britain. For each postcode, Code-Point Open provides a positional quality indicator (PQI), country code, NHS area code along with local government county, district, and ward codes.
This product is updated quarterly
Link any dataset that includes postcode data to the postcode location in a GIS and build up a spatial picture of your data.
To give you extra analytical power, Code-Point Open includes NHS authority and administrative unit codes.
Code-Point Open provides accurate coverage of the 1.7 million postcodes in Great Britain that is updated quarterly.
Access: Download
Data theme: Administrative and Statistical Units
Data structure: Vector - Points
Coverage: Great Britain
Scale: 1:1 250 to 1:10 000
Format: CSV, GeoPackage
Ordering area: All of Great Britain
Publication months: February, May, August, November
OS Data Hub plan: OS OpenData Plan (FREE), Public Sector Plan, Premium Plan, Energy & Infrastructure Plan
Northern Ireland postcodes aren’t included in Code-Point Open, but they are present in Code-Point.
Code-Point is created by taking the average of the coordinates of all the individual addresses in a postcode (provided we have any of sufficient quality), then snapping to the nearest of those addresses. Code-Point then delivers the coordinates of that address, as representative of the whole postcode, to a resolution of 1 metre.
The accuracy of a Code-Point Open record could be expressed as, that the coordinated position will always be within the notional geographical extent of the postcode. The accuracy of each postcode unit coordinate pair is defined by the positional quality indicator (PQI) which provides a quality statement of a Code-Point record.
Access to OS OpenData is free through the OS Data Hub.
GeoPackage is an open, standard, platform-independent, portable, self-describing, compact format for transferring geospatial information. For more information on this format, please see the .
The following tables give a comparison between the CSV attributes and the GeoPackage attribution:
Those fields containing text (A) will be enclosed by double quotes which have not been included in the sizes listed in the table above. An asterisk (*) denotes variable length.
Fields with null data will appear as "" for text and 0 for numeric.
Each record will be terminated with a carriage return character (ASCII 13) and a line feed character (ASCII 10).
Example of a Code-Point Open CSV record:
"SO16 0AS",10,437292,115542,"E92000001","E19000002","E18000009","E10000014","E07000093","E05012936"
Note that there are no Eastings or Northings in GeoPackage; the geometry is already created in the GeoPackage container and is not listed as data but will be seen as a column in a database (PostGIS) called geometry with a coordinate reference system of British National Grid
EPSG: 27700 for Great Britain (GB) postcodes.
Fields with a null value will appear as [Null] for text (PostGIS) or as an empty field in a GIS. A null numeric value will appear as 0 in both a database and an attribute table in a GIS.
Example of a Code-Point Open GeoPackage record taken from the Information tool in QGIS:
Ordnance Survey measures the data in its products in one or more of the ways set out in the definitions of data measures table below.
Data measure | Definition | Sub-measure | Definition |
---|
* When testing the data according to the dataset specification against the ‘real world’ or reference dataset.
Metadata, which is ISO 19115 UK GEMINI 2 compliant, can be found at https:// Metadata .xml files can be found at
The data can be loaded into several geographic information systems (GIS). This section describes how to load the combined CSV output file (for more information on how to combine multiple CSV files, see Section 3.1) into four commonly used GIS, including:
QGIS
ArcGIS Pro
ArcMap
MapInfo Pro 2019
addressed premise
A permanent or non-permanent building structure with an address being a potential delivery point for Royal Mail. Examples of an addressed premise would be a house, a flat within a block of flats, a caravan site, a bollard to which several houseboats may be moored, or an organisation occupying the whole building.
building
A physical, walled structure connected to foundations that has, or will have, a roof. This definition includes buildings surveyed at foundation stage.
CPLC (Code-Point location coordinate)
A National Grid reference for each postcode unit. It is a two-dimensional coordinated point to a resolution of 1 metre. Coordinates are attributed from Gridlink using an accuracy hierarchy.
Country code
The code used by the Office of National Statistics to indicate the country in which the Code-Point georeference lies. This has replaced the PAF update date field.
Country Code
England: E92000001 Scotland: S92000003 Wales: W92000004 N Ireland: N92000002
Comma-separated values (CSV)
The CSV file format is commonly used to exchange data between different applications, for example, Microsoft Excel and Access. Being text files, CSV files can also be viewed in Notepad.
delivery point
A Royal Mail-defined point to which mail is delivered. This may be a property (private address), organisation, mailbox or even, very rarely, the name of an individual. These categories are derived from the Programmers’ Guide from Royal Mail. This is distinct from the addressed premise because there may be more than one organisation at an address.
Gridlink
Gridlink is the name given to a joined-up Government initiative involving Royal Mail, the Office for National Statistics, National Records of Scotland (NRS), Land & Property Services and Ordnance Survey. All these organisations are involved in the georeferencing of postcodes and the relating of postcodes to administrative and National Health Service areas and so on.
inward code or incode
See postcode.
matched address
An address, resulting from a match between the OS MasterMap Topography Layer data and PAF, which has been allocated a coordinate position. The match may be a result of either manual or automatic matching, the latter encompassing both full and ‘fuzzy logic’ matching.
National Grid reference (NGref)
The National Grid provides a unique reference system that can be applied to all Ordnance Survey maps of Great Britain. The map of Great Britain is covered by 100 km by 100 km grid squares, with the origin lying to the west of the Isles of Scilly. When a National Grid reference is quoted, the easting (left to right direction) is always given before the northing (upwards direction). A National Grid reference (to 1 metre) will identify the spatial position of the CPLC.
non-geographic postcodes
Special non-geographic postcodes are allocated to single organisations who receive an exceptionally large amount of mail. These are included in Code-Point Open.
outward code or outcode
See postcode.
Postcode Address File (PAF)
PAF now contains the postal addresses and postcodes of approximately 28 million delivery points in Great Britain.
Postal Address Location Feed (PALF)
The PAL Feed is provided to Ordnance Survey from GeoPlace, who have geocoded the PAF feed from Royal Mail, using source coordinates from Local Authorities in England, Wales & Scotland and Ordnance Survey.
positional quality indicator (PQI)
The positional quality indicator is a flag used to indicate the positional accuracy of the coordinates allocated to each postcode record. There are seven PQI values for the positional quality of CPLCs.
postal address
A postal address is a delivery point that is currently receiving mail. There may be many delivery points within an individual building structure as shown in OS MasterMap Topography Layer data.
postcode
An abbreviated form of address made up of combinations of between six and eight alphanumeric characters. A postcode may cover between 1 and 100 addresses. The average number of addresses per postcode is 15.
postcode area
An area given a unique alphabetic coding by Royal Mail to facilitate the delivering of mail. The area is identified by one or two alpha characters at the start of the full postcode, the letters being derived from a town, city or district falling within the postcode area. There are, at present, 120 postcode areas in Great Britain, for example, SO for Southampton, MK for Milton Keynes, B for Birmingham or W for London West. The postcode area code constitutes the first part of the outward code.
postcode district
A sub-area of the postcode area, specified by the character sub-string within the first half of a full postcode, which may be numeric, alphabetic or alphanumeric; for example, 42 from MK42 6GH or 1A from W1A 4WW. There are approximately 2 986 postcode districts in Great Britain. Note: There are certain non-geographic districts. In these instances, a district code is allocated to cover all large users in the postcode area.
postcode sector
A sub-area of a postcode district, whose area is identified by the number third from the end of a full postcode. There are approximately 11 200 postcode sectors in Great Britain. An example of a postcode sector code is 3, from GU12 3DH.
postcode unit
A sub-area of a postcode sector, indicated by the two letters of the inward postcode, which identifies one or more small-user postcode delivery points or an individual large-user postcode. There are approximately 1.7 million postcode units in the UK.
Description | Data type |
fid | int |
postcode | TEXT |
positional_quality_indicator | int |
N/A | N/A |
country_code | TEXT |
nhs_regional_ha_code | TEXT |
nhs_ha_code | TEXT |
admin_county_code | TEXT |
admin_district_code | TEXT |
admin_ward_code | TEXT |
Mnemonic | Description | Data type | Size |
N/A | N/A | N/A | N/A |
PC | Postcode | A8 | 8 |
PQ | Positional_quality_indicator | I2 | 2 |
EA | Eastings | I6 | * |
NO | Northings | I7 | * |
CY | Country_code | A9 | 9 |
RH | NHS_regional_HA_code | A9 | 9 |
LH | NHS_HA_code | A9 | 9 |
CC | Admin_county_code | A9 | 9 |
DC | Admin_district_code | A9 | 9 |
WC | Admin_ward_code | A9 | 9 |
Completeness | Presence and absence of features against the specified data content | Omission | Features representing objects that conform to the specified data content but are not present in the data. |
Commission | Features representing objects that do not conform to the specified data content but are present in the data. |
Logical consistency | Degree of adherence to logical rules of data structure, attribution and relationships | Conceptual consistency | How closely the data follows the conceptual rules (or model). |
Domain consistency | How closely the data values in the dataset match the range of values in the dataset specification. |
Format consistency | The physical structure (syntax): how closely the data stored and delivered fits the database schema and agreed supply formats. |
Topological consistency | The explicit topological references between features (connectivity) – according to specification. |
Positional accuracy | Accuracy of the position of features | Absolute accuracy | How closely the coordinates of a point in the dataset agree with the coordinates of the same point on the ground (in the British National Grid reference system). |
Relative accuracy | Positional consistency of a data point or feature in relation to other local data points or features within the same or another reference dataset. |
Geometric fidelity | The ‘trueness’ of features to the shapes and alignments of the objects they represent*. |
Temporal accuracy | Accuracy of temporal attributes and temporal relationships of features | Temporal consistency | How well-ordered events are recorded in the dataset (lifecycles). |
Temporal validity (currency) | Validity of data with respect to time: the amount of real-world change that has been incorporated in the dataset that is scheduled for capture under current specifications. |
Thematic accuracy | Classification of features and their attributes | Classification correctness | How accurately the attributes within the dataset record the information about objects*. |
This technical specification provides detailed technical information about Code-Point Open. It is targeted at technical users and software developers.
Code-Point Open is a dataset that contains postcode units for Great Britain, 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.
This document contains additional theoretical information related to Code-Point Open. All users will find the Product Information document useful and informative.
Code-Point Open locates over 1.7 million postcode units for Great Britain, 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.
With each coordinate point, the Code-Point Open product provides:
A postcode
A positional quality indicator (PQI), which indicates the quality of the data underlying the Code-Point location coordinate (CPLC)
The country code (either England, Scotland or Wales)
The National Health Service (NHS) region and area codes
The local government county, district and ward codes
Code-Point Open 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
Postcodes are stored in Code-Point Open 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:
Outcode | Incode | ||
---|---|---|---|
When used in an address, the incode is always separated from the outcode by a single space. 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.
Outcode | Incode | Example postcode | Number of characters in the example postcode |
---|---|---|---|
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 Open 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 product's Technical Specification.
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.
Attribute | Description |
---|---|
An asterisk (*) indicates that the attribute is blank when the entity does not have a code. The Welsh Local Health Boards are included in Code-Point Open.
Each postcode unit location – also known as CPLC (Code-Point Location Coordinate) – is coordinated on the respective National Grid, with Eastings and Northings quoted to a resolution of 1m. The accuracy of each postcode unit coordinate pair is defined by the positional quality indicator (PQI), which provides a quality statement of that Code-Point Open record. There are seven PQI values for the positional quality:
PQI | Description |
---|---|
Glossary Term | Definition |
---|
For guidance on using the product in GeoPackage format, please see the.
NW
6
4
DP
Area
District
Sector
Unit
AN
NAA
M2 5BQ
6
ANN
NAA
M34 3AB
7
AAN
NAA
DN5 7XY
7
AANN
NAA
DN16 9AA
8
ANA
NAA
W1A 4WW
7
AANA
NAA
EC1A 1HQ
8
Postcode
Contains elements for postal area, district, sector, and unit.
Positional quality indicator (PQI)
A flag used to indicate the positional accuracy of the coordinates allocated to each postcode record.
Easting
Distance in metres east of National Grid origin.
Northing
Distance in metres north of National Grid origin.
Country code
Code used by the Office for National Statistics (ONS) to identify the country in which the Code-Point Open georeferenced coordinates lies.
NHS regional health authority code
English Pan Strategic Health Authority in which Code-Point Location Coordinate (CPLC) falls.
NHS health authority code
English Strategic Health Authority or Scottish Health Board in which CPLC falls.
Administrative county code*
County in which CPLC falls.
Administrative district code*
Unitary Authority, Metropolitan and Non-Metropolitan District, London Borough, or Scottish Council Area in which CPLC falls.
Administrative ward code*
Electoral Ward or Division in which CPLC falls.
10
Within the building of the matched address closest to the postcode mean determined automatically by Ordnance Survey.
20
As above but determined by visual inspection by National Records of Scotland (NRS).
30
Approximate to within 50m of the true position (postcodes relating to developing sites may be within 100m of true position).
40
The mean of the positions of addresses previously matched in PALF but which have subsequently been deleted or recoded (very rarely used).
50
Estimated position based on surrounding postcode coordinates, usually to 100m resolution, but 10m in Scotland.
60
Postcode sector mean.
90
No coordinates available.
addressed premise | A permanent or non-permanent building structure with an address being a potential delivery point for Royal Mail. Examples include a house, a flat within a block of flats, a caravan site, or an organisation. |
building | A physical, walled structure connected to foundations that has, or will have, a roof. This includes buildings surveyed at foundation stage. |
CPLC (Code-Point location coordinate) | A National Grid reference for each postcode unit. It is a two-dimensional coordinate point to a resolution of 1 metre. Coordinates are attributed from GridLink using an accuracy hierarchy. |
Country code | The code used by the Office of National Statistics to indicate the country in which the Code-Point georeference lies. This has replaced the PAF update date field. |
Country Code | England: E92000001 Scotland: S92000003 Wales: W92000004 N Ireland: N92000002 |
Comma-separated values (CSV) | The CSV file format is commonly used to exchange data between different applications, for example, Microsoft Excel and Access. Being text files, CSV files can also be viewed in Notepad. |
delivery point | A Royal Mail-defined point to which mail is delivered. This may be a property (private address), organisation, mailbox, or even, very rarely, the name of an individual. |
GridLink | A joined-up Government initiative involving Royal Mail, the Office for National Statistics (ONS), National Records of Scotland (NRS), Land & Property Services, and Ordnance Survey. |
inward code or incode | See postcode. |
matched address | An address resulting from a match between the OS MasterMap Topography Layer data and PAF, which has been allocated a coordinate position. |
National Grid | A unique referencing system that can be applied to all Ordnance Survey maps of Great Britain (GB) at all scales. |
National Grid reference (NGref) | The National Grid provides a unique reference system that can be applied to all Ordnance Survey maps of Great Britain. The map of Great Britain is covered by 100 km by 100 km grid squares. |
non-geographic postcodes | Special non-geographic postcodes are allocated to single organisations who receive an exceptionally large amount of mail. These are included in Code-Point Open. |
outward code or outcode | See postcode. |
Postcode Address File (PAF) | PAF now contains the postal addresses and postcodes of approximately 28 million delivery points in Great Britain. |
Postal Address Location Feed (PALF) | The PAL Feed is provided to Ordnance Survey from GeoPlace, who have geocoded the PAF feed from Royal Mail, using source coordinates from Local Authorities in England, Wales, and Scotland. |
positional quality indicator (PQI) | The positional quality indicator is a flag used to indicate the positional accuracy of the coordinates allocated to each postcode record. There are seven PQI values for the positional quality of CPLCs. |
postal address | A postal address is a delivery point that is currently receiving mail. There may be many delivery points within an individual building structure as shown in OS MasterMap Topography Layer data. |
postcode | An abbreviated form of address made up of combinations of between six and eight alphanumeric characters. A postcode may cover between 1 and 100 addresses. The average number of addresses per postcode is 15. |
postcode area | An area given a unique alphabetic coding by Royal Mail to facilitate the delivering of mail. The area is identified by one or two alpha characters at the start of the full postcode. |
postcode district | A sub-area of the postcode area, specified by the character sub-string within the first half of a full postcode, which may be numeric, alphabetic, or alphanumeric. |
postcode sector | A sub-area of a postcode district, whose area is identified by the number third from the end of a full postcode. |
postcode unit | A sub-area of a postcode sector, indicated by the two letters of the inward postcode, which identifies one or more small-user postcode delivery points or an individual large-user postcode. |