IMPACT OF GRIDLINK ON USERS OF ONS POSTCODE LOCATION PRODUCTS

Transcription

1 IMPACT OF GRIDLINK ON USERS OF ONS POSTCODE LOCATION PRODUCTS 1. Introduction 1.1 Gridlink is a high quality postcode-based dataset created by a consortium comprising the Office for National Statistics (ONS), Ordnance Survey (OS), Royal Mail (RM), Ordnance Survey of Northern Ireland (OSNI) and the General Register Office for Scotland (GROS). The Gridlink initiative overcomes issues of duplicated effort and inconsistent standards as Gridlink data are being incorporated into the various respective outputs produced by the individual Consortium members (eg. the ONS postcode directories, OS's CodePoint, RM's UK Addresses TM ). 1.2 A well-defined Gridlink data production process, requiring regular monthly data flows between the various organisations, has been developed and implemented which will ensure data are consistent and meet the high standards required by users/customers. The production process, built around a Gridlink Master base maintained by OS, will deliver the core postcode location data to the Consortium members for incorporation in their respective customer products. 1.3 The data items comprising the Gridlink dataset are 1 : All current (ie. 'live') UK unit postcodes. Grid references 2 to 1 metre resolution (which allows truncated grid references to 10 metre or 100 metre resolution to be provided). Positional quality indicators for grid references 3. UK country codes. Administrative electoral ward codes 4. Administrative local authority district codes 4. Administrative unitary authority codes 4. Administrative county codes 4. Health regional office area codes. Health area codes. 1.4 The Gridlink initiative was launched at the AGI 2000 Conference at the end of September and the products sourced from Gridlink have been released since November Accessing geographic data 2.1 As there are differences in the ways ONS internal users and its external customers will access Gridlink data it is necessary to clarify these differences before describing the impacts of Gridlink data which will be felt similarly by both sets of users/customers Not all areas shown exist in all four UK constituent countries. Postcodes in GB are referenced to the GB grid system and postcodes in Northern Ireland are referenced to the separate Irish grid system. Most of the area codes are being assigned using surveyed postal addresses (ie. with precise grid references) but there will be some postcodes for which area codes will necessarily be assigned using grid references imputed by ONS Geography until such time as surveyed data becomes available. The administrative area code is a single code that contains elements for electoral wards, local authority districts and counties or for electoral wards and unitary authorities.

2 2.2 ONS Geography maintains a corporate geographic database which is accessed directly by some ONS internal users. The database is also used to produce a range of postcode directories which meet the preferred requirements of other internal users and which are also supplied to ONS's external customers. 2.3 Rather than create a new geographic database to accommodate Gridlink data, the existing database has been extended. Consequently, the database now comprises some duplicate fields (eg. health authority codes assigned to postcodes using the ONS clerically checked or imputed methodology and also the same range of health authority codes assigned to postcodes within OS as part of the Gridlink production system using a common 'point-in-polygon' methodology). 2.4 By extending its geographic database, ONS Geography is able to continue to produce postcode directories containing data created by the 'old-style' methodology or it can equally easily produce postcode directories containing Gridlink data and other geographic data derived from Gridlink data. 2.5 Although there are differences in the way geographic data are accessed the impacts of moving to Gridlink data will be the same. However, ONS users accessing the ONS Geography database will need to exercise care to ensure they are accessing the data fields they require and other internal users and all external customers will need to ensure they specify which type of postcode directory they require - 'old style' or Gridlink. Postcode directories produced from either methodology will be available for a limited period - see Section To simply matters in the rest of the paper, 'old-style' and 'Gridlink-based' will be used to describe the postcode directory variations and their respective production systems (though in reality, as already explained, there is only a single corporate geography database and a single postcode directory production system). 3. Differences between Gridlink-based and 'old style' postcode location data 3.1 Although a policy of continuity has been adopted as far as possible in moving from the 'old style' postcode directory production system to a Gridlink-based system there are, inevitably, some differences, due mainly to methodological differences in assigning grid references and area codes. 3.2 Grid references The grid references now generally available to users within ONS under the Gridlink initiative are to 1 metre resolution (as opposed to 10/100 metre resolution which was routinely available previously). Usually external customers will be supplied with 100 metre resolution grid references though 1 metre resolution references are available at increased cost to cover the royalties payable to OS/OSNI The grid references are all numeric, whereas in the 'old style' system a single alpha character (representing two numeric characters) was used in the Northing in the north of Scotland to overcome the additional numeric character that would otherwise be required to cover such an area Separate 'Easting' and 'Northing' fields in Gridlink-based system have replaced the single grid reference field in the 'old style' system The grid reference status indicators (now termed 'positional quality indicators (PQIs)') are primarily allocated during the Gridlink Master base processing within OS and represent a range of positional qualities. An extended range of indicators is now being used:

3 1 - within the building of the matched address closest to the postcode mean; 2 - as for status value 1, except by visual inspection of Landline TM maps (Scotland only); 3 - approximate to within 50 metres; 4 - postcode unit mean (mean of matched addresses with the same postcode, but not snapped to a building); 5 - imputed by ONS, by reference to surrounding postcode grid references; 6 - postcode sector mean (mainly PO Boxes); 7 - not allocated; 8 - postcode terminated prior to Gridlink initiative, last known ONS postcode grid reference; 9 - no grid references available; 0 - not allocated ONS data files retain 'terminated postcodes' (which is a feature not adopted elsewhere in the Consortium). OS-assigned grid references for postcodes that are terminated are not yet routinely available (as no postcodes have been terminated since the start of the Gridlink initiative) and so the grid references held in the 'old style' system for terminated postcodes are being made available in Gridlink-based outputs. Conversely, in 137,000 instances where terminated postcodes have been replaced by new postcodes on a one-for-one basis (as part of postcode re-organisations) the area information and the associated PQIs for the 're-organised' postcode have been copied back to the terminated postcode. In due course, as postcodes with grid references assigned by OS are terminated, the original OS-assigned grid references will remain in all Gridlinkbased outputs with the appropriate PQIs A single PQI (value 8) is being used to indicate grid references assigned to terminated postcodes by ONS - see also Area codes A single 'point-in-polygon' methodology for assigning area codes to postcodes has been adopted in the Gridlink-based system which depends on the use of OS's Boundary-Line product in conjunction with each postcode's grid reference. The consequence is that there is no longer a requirement to hold a status indicator representing the accuracy of the area assignments as their accuracy is derived from the accuracy of the grid references The Gridlink-based system depends on the use of OS s Boundary-Line (and data to a similar standard supplied by OSNI) and so the currency of the area code assignments reflects the particular version of Boundary-Line used. The old style postcode directory production system depends on boundary change processing undertaken by ONS Geography in respect of areas in England and Wales and on input files provided by GROS in respect of Scottish areas; there is no equivalent requirement for a regular input file from OSNI in respect of areas in Northern Ireland as their boundaries rarely change. At the present time, GROS have not had the resources available to provide an input file to reflect the significant ward boundary changes occurring in April 1999 and so the Scottish part of the old style postcode directory is currently deficient at electoral ward level and will differ significantly from a Gridlink-based postcode directory. 4. Impacts of the changes for users/customers 4.1 As explained in 3.1, users/customers are not expected to see many changes. The few changes are detailed below.

4 4.2 Grid reference format A 6 character all numeric character 1 metre resolution Easting grid reference field and a 7 character all numeric character 1 metre resolution Northing grid reference field in Gridlink outputs have superseded the single 10 alpha/numeric character 10 metre resolution grid reference field on the 'old style' system. Where a 100 metre resolution grid reference is continued to be required, for example by NHS Postcode Directory customers, (ie. a 4 character Easting and a 5 character Northing) a blank field will be included on postcode directories to retain each postcode's record length. 4.3 Grid reference Positional Quality Indicators Apart from the changes to the range of PQIs provided, and their representation of accuracy, the use of a single PQI for grid references assigned by ONS for terminated postcodes supersedes the range of 4 status indicators previously included on its postcode directories which will no longer be routinely available on the Gridlink outputs. The original indicators will, however, be available within ONS Geography to service any enquiries. 4.4 Ward code status indicators As already explained in 3.3.1, there is no requirement to continue to hold ward code indicators so the field is blank on postcode directories produced from Gridlink. 4.5 Allocation of area information to postcodes The single methodology being applied to the assignment of grid references to postcodes within the Gridlink initiative will inevitably cause the grid references of some postcodes to differ from those in the 'old style' outputs. This will, also inevitably, cause some postcodes to be assigned to different areas to those available on postcode directories produced from the 'old style' system; consequently, users will need to exercise some caution in moving from one system to another as this may cause some variations in statistical outputs which are not reflected by changes 'on the ground'. The differences in the assignments of postcodes to Scottish electoral wards are particularly severe for the reasons outlined in para When assessing the impact of moving to the Gridlink system on their respective statistical outputs, users/customers will also need to be mindful, in their relationships with other business areas/external organisations using postcode data files, of the impact should such business areas/external organisations decide not to move to Gridlink-based data simultaneously as their respective outputs may differ due to the source of postcode location data. Parallel running should minimise any adverse impact - see section 5 - but users/customers should satisfy themselves about compatibility in such circumstances Many other geographies linked to postcodes which are supported by ONS Geography depend on the links between postcodes and electoral wards. As such links may be affected by the methodological changes it follows that some postcode links to the other geographies may be similarly affected Once customers move to Gridlink-based outputs there may, in some instances, be a further impact on the allocation of postcodes to grid references and the consequential impact on other geographies. The methodology for assigning grid references to postcodes (ie. the most accurate assignments) is to identify the grid references of all the addresses (delivery points) in each postcode to establish a postcode mean and to find the nearest matched address. If the delivery points within a postcode change (due to development/demolition) there may be an impact on the postcode mean which might affect the administrative areas assigned to postcodes, but without there having been any substantive change to the postcode 'boundary'.

5 4.5.5 Clearly, improvements to the quality of grid references will also impact on the assignment of area codes to postcodes, but this has always been the case in attempting to provide continually-improved data quality. 4.6 Annual updating of area information Area information reflecting boundary changes in any given year is added to the 'old style' system at the end of the calendar year and the first postcode directories made available containing the updated area information are released in February of the following year. However, the Gridlink system is dependent on Boundary-Line to achieve the annual update and, under normal conditions, Boundary-Line is available in October. The consequence is that updated area information for any given year could be available on postcode location data extracted from the Gridlink system in November. This will suit those users/customers who wish to update their data at the earliest possible time but there will be other customers who process their data after the end of the given year who would not require an early update of the Gridlink system. This was not a problem in 2000 as Boundary-Line was produced behind schedule and so the first postcode directories containing 2000 area information were not be available until February 2001 (ie. no change to the 'old style' system) A further impact is that if Boundary-Line is produced in October there will not be any opportunity to include any boundary changes that are operative late in the year. Whilst such changes are rare, there were a number of instances in 1998 and 1999 where ward boundaries were affected by the provisions of Parish Orders operative in November. It is not known whether 'late' Orders will continue to be made in future nor, if so, the extent of the impact on boundaries of interest to users/customers. ONS Geography routinely maintains a list of all known future Orders and will be able to offer appropriate advice/guidance based on any available information ONS Geography has recognised the potential difficulties raised by the current irregular availability of Boundary-Line. ONS Geography also maintains a 'shadow' system which is used to apply all data changes (to prevent the corruption of the regular outputs from subsequent changes) and which will meet the requirement of those users/customers who do not require annual updates to be applied before the end of the year. ONS Geography will routinely monitor the quality and timing of Boundary-Line and in the event that the product is delayed beyond January of the following year, will notify all users/customers and agree the appropriate action to be taken to meet their specific requirements. 5. Parallel running 5.1 Whilst ONS Geography does not wish to continue to support two systems it recognises that: - its many users/customers will need time to migrate to the new system and will need to fully assess the impacts in their respective business areas, and possibly those of other business areas/external organisations, before making changes; and - the new system depends significantly on the regular data flows between the Gridlink Consortium members necessary to deliver monthly Gridlink data and OS's ability to produce timely and accurate Boundary-Line to enable areas to be assigned to postcodes. Consequently, to support users/customers and for contingency against any failure by the Consortium to deliver Gridlink data, ONS Geography will continue to support both systems.

6 5.2 Whilst no time period has been set for parallel running, clearly ONS Geography would wish this period to be as short as possible. It is hoped that ONS Geography's internal users and its external customers will migrate to Gridlink-based geographic data and Gridlink-based postcode directories are being routinely supplied with any continuing requests for directories produced from the 'old style' system. In the meantime, ONS Geography will continue to monitor the provision of Gridlink data and the production of Boundary-Line and when it is satisfied that there is no longer a requirement to maintain a 'old style' system for contingency it will plan to remove support for the 'old style' system, taking suitable account of the views of its users/customers - as far as is reasonable and practicable. 6. File specification 6.1 File specifications of postcode directories produced from the parallel systems are attached - Annex A: 'Gridlink' system; Annex B: 'old style' system. 7. Contacts 7.1 Fuller information about the availability and contents of the ONS geographic database and postcode directories can be obtained from: ONS Geography Customer Support Unit Office for National Statistics Segensworth Road FAREHAM PO15 5RR Tel: GTN: Fax: ons.geography@ons.gov.uk A C Taylor Geography Services Manager ONS Geography 31 May 2001 (version 3)

7 Annex A ALL FIELDS POSTCODE DIRECTORY RECORD SPECIFICATION containing Gridlink core components Length 7 Unit postcode 7 character version 8 Unit postcode 8 character version 6 Date of introduction 6 Date of termination AB1D1AA- ZE999ZZ AB1DD1AA- ZE99D9ZZ YYYYMM - year and month YYYYMM - year and month or DDDDDD 2, 3 or 4 character outward code - left aligned; 3 character inward code - right aligned. 3rd and 4th characters may be blank (D). 2, 3 or 4 character outward code - left aligned; 3 character inward code - right aligned. 5th character always, and possibly the 3rd and 4th characters, blank (D ). Most recent occurrence. Most recent occurrence. DDDDDD = live postcode. 2 County 00, or 95 England: 2 digit numeric county code, or 00 preceding unitary authority code; Wales and Scotland: 00 preceding unitary authority code; Northern Ireland: 95; DD (if unitary authority field is also blank) = no information available. 2 Local authority district/unitary authority 2 (Electoral) ward/division 1 Postcode user type AA-MW; NA-PT; QA-RJ; UC-UQ; ranges) AD-ZD or DD FA-ZZ; or DD 0 or 1 0 = small user; 1 = large user. England: 2 digit alpha local authority/ district code or 2 digit alpha unitary authority code; Wales and Scotland: 2 digit alpha unitary authority code; Northern Ireland: single digit alpha district code & D; DD = no information available. Used with county and local authority district/unitary authority code to derive uniqueness. England and Wales: 2 digit alpha code; Scotland and Northern Ireland: 2 digit numeric code; DD = no information available.

8 4, 5 or 6 National grid reference - Easting 5, 6 or 7 National grid reference - Northing 4, 5 or 6 character numeric grid reference or DDDDDD (max) 5, 6 or 7 character numeric grid reference or DDDDDDD (max) GB and Northern Ireland national grid references derived from Ordnance Survey s (GB) ADDRESSPOINT and OS (NI) Compass products. 100 metre, 10 metre and 1 metre resolution grid references available. As above. 1 Grid reference positional quality indicator 1-6, within the building of the matched address closest to the postcode mean; 2 - as for status value 1, except by visual inspection of Landline maps (Scotland only); 3 - approximate to within 50 metres; 4 - postcode unit mean (mean of matched addresses with the same postcode, but not snapped to a building); 5 - imputed by ONS, by reference to surrounding postcode grid references; 6 - postcode sector mean, (mainly PO Boxes); 7 - not allocated; 8 - postcode terminated prior to Gridlink initiative, last known ONS postcode grid reference 5 ; 9 - no grid references available; 0 - not allocated. 3 Health authority/ health board QAA-QZZ* range); SA9-SZ9; YAC-YAF; ZE0-ZW0 or DDD * the last character may be numeric Q = health authorities in England and Wales; S = health boards in Scotland; Y = health authorities in the Channel Islands and the Isle of Man; Z = health boards in Northern Ireland; 5 Customers taking 1 and 10 metre grid references should note that the terminated postcodes with an 8 code are those that had been terminated prior to the Gridlink initiative which became operational in November The grid references are those assigned by ONS for postcodes in England and Wales and those assigned by the General Register Office for Scotland and the Department for Economic Development in Northern Ireland for their respective postcodes. Consequently, the grid references for England and Wales will be mainly to 100 metre resolution while the grid references for other parts of the UK will be to 10 metre resolution. The positional quality indicators previously available on the non-gridlink postcode directories are no longer being made available routinely but they will be held by ONS to service enquiries. Postcodes terminated since November 2000 will retain the same positional quality indicators prior to their termination.

9 3 NHS regional office Y01, Y02, Y07- Y12, W00, S00, Z00 or DDD Y = rgional offices in England; W00 = Wales; S00 = Scotland; Z00 = Northern Ireland; 3 Country 044, 064, 128, 152, 179, 220 or DDD 044 = the Channel Islands; 064 = England; 128 = Isle of Man; 152 = Northern Ireland; 179 = Scotland; 220 = Wales; 1 PO Box/ non-geographic indicator 0-3 or D 0 = neither PO Box or non-geographic postcode; 1 = PO Box postcode; 2 = non-geographic postcode; 3 = PO Box and non-geographic postcode; D = unknown (mostly terminated postcodes for which a postcode type cannot be identified). 1 PAF indicator 1 or D 1 = postcode yet to appear on the Royal Mail s Postcode Address File (PAF); D = postcode obtained from PAF. 1 Government Office for the Region (GOR) A, B, D-H, J, K, W-Y or D A, B, D-H, J and K = GORs in England; W = Wales; X = Scotland; Y = Northern Ireland; D = no information available. 1 Standard (statistical) region (SSR) 1-9 or D 1-8 = former standard statistical regions in England; 9 = (region) code for Wales; D = postcodes not in England or Wales/no information available for postcodes in England or Wales. 3 Parliamentary constituency or DDD (code range contains gaps) England; Wales; Scotland; Northern Ireland; 2 (European) Electoral Region (ER) or DD England; 10 Wales; 11 Scotland; 12 Northern Ireland; DD = no information available.

10 3 Training Enterprise Council/ Local Enterprise Company (TEC/LEC) , W11-W14, S01-S22 or DDD England; W11-W14 Wales; S01-S22 Scotland; TECs (England and Wales); LECs (Scotland); there are no TEC/LECs in Northern Ireland. DDD = postcodes in Northern Ireland/no information available for postcodes in GB. TEC/LEC boundaries are revised annually but are always based on electoral wards existing on 21 April 1991 (Census day). 3 Travel-to-work area (TTWA) or DDD United Kingdom; DDD = no information. Travel-to-work areas are as defined in 1998 and are based on those electoral ward boundaries existing on 21 April 1991 (Census day). 5 Primary Care Group (PCG)/ Local Health Group (LHG)/ Primary Care Trust (PCT) 4AA01-4ZZ99 for PCG/LHG; 5AADD-5ZZDD for PCT; or DDDDD Primary Care Groups/Trusts exist in England; Local Health Groups exist in Wales; there are no equivalents in Scotland or Northern Ireland = PO Boxes or non-geographic postcodes in England and Wales/postcodes in Scotland and Northern Ireland DDDDD = postcodes in the Channel Islands and the Isle of Man/no information for postcodes in England and Wales. 10 NUTS areas 6 UKC UKN ranges) or DDDDDDDDDD England: UKC UKK ; Wales: UKL UKL ; Scotland: UKM UKM ; Northern Ireland: UKN UKN ; DDDDDDDDDD = no information available. Characters 1-3 = NUTS-1 level; characters 1-4 = NUTS-2 level; characters 1-5 = NUTS-3 level; characters 1-7 = NUTS-4 level; characters 1-10 = NUTS-5 level. 6 Nomenclature of Units for Territorial Statistics, a classification of spatial units used within the UK for producing regional statistics for comparison with other regions within the European Union.

11 Census Enumeration District (ED) - England and Wales only Census Enumeration District (ED) - England and Wales only 01AAFA01-07DBHB99; 08UBFA01-63UEHB99 ranges) or DDDDDDDD (National Statistics code range) AAFA01-TTHB99 or DDDDDD (1991 Census code range) 2 digit numeric county code (incl GLC and metropolitan counties), 2 digit alpha district code, 2 digit alpha ward code, 2 digit numeric ED code; no information is provided for Scotland or Northern Ireland; DDDDDDDD = postcodes in Scotland, Northern Ireland, the Channel Islands and the Isle of Man/no information available for postcodes in England and Wales. 2 digit alpha district code, 2 digit alpha ward code, 2 digit numeric ED code; no information is provided for Scotland or Northern Ireland; DDDDDD = postcodes in Scotland, Northern Ireland, the Channel Islands and the Isle of Man/no information available for postcodes in England and Wales. 1 ED positional quality indicator - England and Wales only 1, 2 or D 1 = imputed on the original 1991 ED:Postcode link file; 2 = subsequently imputed for the maintained version of the ED:Postcode link file; D (with an ED code) = original ED assignment using census forms; D (without an ED code) = postcodes in Scotland and Northern Ireland, Channel Islands and the Isle of Man/no information available for postcodes in England and Wales. 4 Address count Numeric count taken from PAF. (Number of addresses excluding small businesses/non-residential.) 4 Delivery point count 4 Multiple occupancy count 4 Small business count 3 Health authority/ health board as at 1 April of previous year QAA-QZZ* range); SA9-SZ9; YAC-YAF; ZE0-ZW0 or DDD * the last character may be numeric Numeric count taken from PAF. (Total number of delivery points.) Numeric count taken from PAF. (Number of households sharing delivery points.) Numeric count taken from PAF. (Number of small businesses.) Q = health authorities in England and Wales; S = health boards in Scotland; Y = health authorities in the Channel Islands and the Isle of Man; Z = health boards in Northern Ireland;

12 3 Local Education Authority (LEA) ; NA-PZ; QA-RZ; 95A-95Z or DDD (code range contains gaps) England: 3 digit numeric code; Wales: 2 digit alpha unitary authority code (NA-PZ) Scotland: 2 digit alpha unitary authority code (QA-RZ) Northern Ireland: 95, single digit alpha district code;

13 Annex B ALL FIELDS POSTCODE DIRECTORY RECORD SPECIFICATION old style/traditional version Length 7 Unit postcode 7 character version 8 Unit postcode 8 character version 6 Date of introduction 6 Date of termination AB1D1AA- ZE999ZZ AB1DD1AA- ZE99D9ZZ YYYYMM - year and month YYYYMM - year and month or DDDDDD 2, 3 or 4 character outward code - left aligned; 3 character inward code - right aligned. 3rd and 4th characters may be blank (D). 2, 3 or 4 character outward code - left aligned; 3 character inward code - right aligned. 5th character always, and possibly the 3rd and 4th characters, blank (D ). Most recent occurrence. Most recent occurrence. DDDDDD = live postcode. 2 County 00, or 95 England: 2 digit numeric county code, or 00 preceding unitary authority code; Wales and Scotland: 00 preceding unitary authority code; Northern Ireland: 95; DD (if unitary authority field is also blank) = no information available. 2 Local authority district/unitary authority 2 (Electoral) ward/division AA-MW; NA-PT; QA-RJ; UC-UQ; ranges) AD-ZD or DD FA-ZZ; or DD England: 2 digit alpha local authority/ district code or 2 digit alpha unitary authority code; Wales and Scotland: 2 digit alpha unitary authority code; Northern Ireland: single digit alpha district code & D; DD = no information available. Used with county and local authority district/unitary authority code to derive uniqueness. England and Wales: 2 digit alpha code; Scotland and Northern Ireland: 2 digit numeric code; DD = no information available. 1 Postcode user type 0 or 1 0 = small user; 1 = large user.

14 4, 5 or 6 National grid reference 10 metres resolution 1 Grid reference status indicator 3 Health authority/ health board 3 NHS regional office 10 character alpha/numeric* grid reference or DDDDDDDDDD * alpha characters appear in the 6 th character for posstcodes in the Hebrides and Shetland Islands 5 digit Easting, 5 digit Northing; DDDDDDDDDD = no information available. * alpha characters O, P, T, U, Y and Z are used where the 100km Northing (in the Ordnance Survey (GB) system) requires 2 numeric characters (ie. 10 and 12). 0-2, 4-7 or D 0 (UK) = assigned clerically; 1, 2 or 4 (GB) = imputed (degrees of confidence vary, 1 is the most accurate); 5 (NI only) = arithmetic mean using OSNI individual geocodes ; 6 = (NI only) = arithmetic mean using individual address geocodes provided by census enumerators (for postcodes wholly contained in an ED); 7 (NI only) = as 6 but for postcodes split by ED boundaries; D (UK) = no information available. QAA-QZZ* range); SA9-SZ9; YAC-YAF; ZE0-ZW0 or DDD * the last character may be numeric Y01, Y02, Y07- Y12, W00, S00, Z00 or DDD 3 Country 044, 064, 128, 152, 179, 220 or DDD 1 PO Box/ non-geographic indicator Q = health authorities in England and Wales; S = health boards in Scotland; Y = health authorities in the Channel Islands and the Isle of Man; Z = health boards in Northern Ireland; Y = Regional offices in England; W00 = Wales; S00 = Scotland; Z00 = Northern Ireland; 044 = the Channel Islands; 064 = England; 128 = Isle of Man; 152 = Northern Ireland; 179 = Scotland; 220 = Wales; 0-3 or D 0 = neither PO Box or non-geographic postcode; 1 = PO Box postcode; 2 = non-geographic postcode; 3 = PO Box and non-geographic postcode; D = unknown (mostly terminated postcodes for which a postcode type cannot be identified).

15 1 PAF indicator 1 or D 1 = postcode yet to appear on the Royal Mail s Postcode Address File (PAF); D = postcode obtained from PAF. 1 Government Office for the Region (GOR) 1 Standard (statistical) region (SSR) 3 Parliamentary constituency 2 (European) Electoral Region (ER) 3 Training Enterprise Council/ Local Enterprise Company (TEC/LEC) 3 Travel-to-work area (TTWA) A, B, D-H, J, K, W-Y or D A, B, D-H, J and K = GORs in England; W = Wales; X = Scotland; Y = Northern Ireland; D = no information available. 1-9 or D 1-8 = former standard statistical regions in England; 9 = (region) code for Wales; D = postcodes not in England or Wales/no information available for postcodes in England or Wales or DDD (code range contains gaps) England; Wales; Scotland; Northern Ireland; or DD England; 10 Wales; 11 Scotland; 12 Northern Ireland; DD = no information available , W11-W14, S01-S22 or DDD England; W11-W14 Wales; S01-S22 Scotland; TECs (England and Wales); LECs (Scotland); there are no TEC/LECs in Northern Ireland. DDD = postcodes in Northern Ireland/no information available for postcodes in GB. TEC/LEC boundaries are revised annually but are always based on electoral wards existing on 21 April 1991 (Census day) or DDD United Kingdom Travel-to-work areas are as defined in 1998 and are based on those electoral ward boundaries existing on 21 April 1991 (Census day).

16 5 Primary Care Group (PCG)/ Local Health Group (LHG)/ Primary Care Trust (PCT) 4AA01-4ZZ99 for PCG/LHG; 5AADD-5ZZDD for PCT; or DDDDD Primary Care Groups/Trusts exist in England; Local Health Groups exist in Wales; there are no equivalents in Scotland or Northern Ireland = PO Boxes or non-geographic postcodes in England and Wales/postcodes in Scotland and Northern Ireland DDDDD = postcodes in the Channel Islands and the Isle of Man/no information for postcodes in England and Wales. 10 NUTS areas 7 UKC UKN ranges) or DDDDDDDDDD England: UKC UKK ; Wales: UKL UKL ; Scotland: UKM UKM ; Northern Ireland: UKN UKN ; DDDDDDDDDD = no information available. Characters 1-3 = NUTS-1 level; characters 1-4 = NUTS-2 level; characters 1-5 = NUTS-3 level; characters 1-7 = NUTS-4 level; characters 1-10 = NUTS-5 level Census Enumeration District (ED) - England and Wales only Census Enumeration District (ED) - England and Wales only 01AAFA01-07DBHB99; 08UBFA01-63UEHB99 ranges) or DDDDDDDD (National Statistics code range) AAFA01-TTHB99 or DDDDDD (1991 Census code range) 2 digit numeric county code (incl GLC and metropolitan counties), 2 digit alpha district code, 2 digit alpha ward code, 2 digit numeric ED code; no information is provided for Scotland or Northern Ireland; DDDDDDDD = postcodes in Scotland, Northern Ireland, the Channel Islands and the Isle of Man/no information available for postcodes in England and Wales. 2 digit alpha district code, 2 digit alpha ward code, 2 digit numeric ED code; no information is provided for Scotland or Northern Ireland; DDDDDD = postcodes in Scotland, Northern Ireland, the Channel Islands and the Isle of Man/no information available for postcodes in England and Wales. 7 Nomenclature of Units for Territorial Statistics, a classification of spatial units used within the UK for producing regional statistics for comparison with other regions within the European Union.

17 1 ED positional quality indicator - England and Wales only 4 Address count Delivery point count 4 Multiple occupancy count 4 Small business count 3 Health authority/ health board as at 1 April of previous year 3 Local Education Authority (LEA) 1, 2 or D 1 = imputed on the original 1991 ED:Postcode link file; 2 = subsequently imputed for the maintained version of the ED:Postcode link file; D (with an ED code) = original ED assignment using census forms; D (without an ED code) = postcodes in Scotland and Northern Ireland, Channel Islands and the Isle of Man/no information available for postcodes in England and Wales QAA-QZZ* range); SA9-SZ9; YAC-YAF; ZE0-ZW0 or DDD * the last character may be numeric ; NA-PZ; QA-RZ; 95A-95Z or DDD (code range contains gaps) Numeric count taken from PAF. (Number of addresses excluding small businesses/non-residential.) Numeric count taken from PAF. (Total number of delivery points.) Numeric count taken from PAF. (Number of households sharing delivery points.) Numeric count taken from PAF. (Number of small businesses.) Q = health authorities in England and Wales; S = health boards in Scotland; Y = health authorities in the Channel Islands and the Isle of Man; Z = health boards in Northern Ireland; England: 3 digit numeric code; Wales: 2 digit alpha unitary authority code (NA-PZ) Scotland: 2 digit alpha unitary authority code (QA-RZ) Northern Ireland: 95, single digit alpha district code;