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This publication is available at https://www.gov.uk/government/publications/national-polygon-dataset-specification/national-polygon-dataset-specification
This is the published dataset of HM Land Registry Index Polygons. Index Polygons are a representation of a registered title showing its location and extent.
The title plan and register record the general position of the boundaries of a registered title (unless shown as having been determined as an exact boundary in accordance to section 60, Land Registration Act 2002.
An index polygon is part of the Index referred to in section 68, 2002 Land Registration Act and rule 10, Land Registration Rules 2003. Its purpose is to provide an index to show the indicative location of a registered title. Index polygons are held in vector format.
The title plan and register share the same ID called the Title Number. Every registered title has at least one index polygon. An index polygon has a unique Polygon ID (Poly_ID). The relationship between the registered title and index polygon(s) is managed through the title number.
HM Land Registry Index Polygons are mapped against Ordnance Survey large scale data, MasterMap, Index Polygons will follow features in MasterMap where those features relate to the ownership boundary. Ownership boundaries do not always follow features mapped in MasterMap.
2. Specification scope
|Polygons||HM Land Registry’s Index Polygons|
|Coordinate reference system||British National Grid (EPSG:27700)|
2.1 Relationship to other HM Land Registry dataset
The National Polygon Dataset is the published dataset of Index polygons for England and Wales. Each index polygon contains a title number to enable the polygons to be linked to the Title Descriptor and UPRN datasets. The separation of this data into three data sets means that each data set is smaller and easier to handle and that data currency and updates can be more simply managed.
The INSPIRE Index Polygons are a sub-set of the National Polygon dataset, made up of polygons related to freehold titles. INSPIRE Index Polygons have a much simpler set of attributes, describing the polygon unique identifier, the polygon create date and the polygon last updated date.
Relationships can be made between the National Polygon Dataset and other information in the title register by linking via the title number.
3. Data product identification
HM Land Registry are mandated to create an index polygon for each title registration as described in section 68, 2002 Land Registration Act and rule 10, Land Registration Rules 2003.
The purpose of the index polygon is to show the location of a registered title, to general boundaries and in context of HM Land Registry practice.
The National Polygon Dataset (NPD) is a data product to enable HM Land Registry customers to efficiently locate the indicative ownership extent of registered titles across England and Wales. The data can be used in a geographic information system (GIS) to view and query title index extents.
The data contains a title number to enable relationships to be made between the NPD and other HM Land Registry data. The data also includes the Title Descriptor and UPRN datasets which describes the relationship between the NPD polygons and the Unique Property Reference Number (UPRN) from AddressBase. This means that customers can use the UPRN to make relationships between NPD and other central and local Government data that uses AddressBase UPRN’s.
3.2 Spatial representation
Data is available as vector polygons.
3.3 Spatial resolution
Polygons captured against the Ordnance Survey large scale map at a scale of 1:1,250, 1:2,500 and 1:10,000 dependent upon the scale of OS MasterMap.
4. Data content and structure
The class diagram below defines the geometry and attribute content of a HM Land Registry index polygon.
4.1 Table 1: NPD class diagram
4.2 Table 2: NPD table structure
|Field Name||Data Type||Mandatory?||Description|
|Shape||Geometry||Yes||Geometry of the Index Polygon must be a single area|
|Poly_ID||Number||Yes||Unique polygon reference. Identifier is unique to spatial object and managed through lifecycle rules for the dataset|
|Title_No||Character||Yes||Identifier of the title registration, required to enable associations to be made with the text register|
|INSERT||Text||Yes||Date on which the polygon in the title was initially created on the index map|
|UPDATE||Text||Yes||Date on which all or part of the title was last updated|
|Rec_Status||Character||Yes||Identifier to describe status of the polygon. Added (A), Changed (C), Deleted (D)|
5. Data quality
The National Polygon Dataset contains a number of known issues, including:
- small sliver gaps and overlaps
- technical overlapping polygons (polygons where small overlaps exist due to mapping inconsistencies, that do not describe a real conflict of registered titles)
- actual overlaps, where two or more registered titles include the same land/property and will be resolved upon application
The data also contains data types that facilitate the process of Land Registration and are a real managed part of the data model but could be considered an issue if the data is not understood, these feature types are explained further on in the document.
The data has been captured for the purposes of enabling land registration, and thus has evolved to be fit for our purpose and the processes and tools that we use.
We welcome feedback on any data quality issues.
6. Data capture information
An index polygon is a representation of the title extent. HM Land Registry practice allows for an index polygon extent to be the same size, larger or smaller than the extent shown on a title plan. This means that index polygons cannot and should not be relied upon as showing the extent of registered titles. Practice has been reviewed and changed over many years, the index polygon dataset includes polygons based on former practice(s) and does contain inconsistencies.
Index polygons were manually captured on OS county series sheets, national grid sheets and parcels books.
HM Land Registry implemented its computer mapping system (production environment) in 2001, and all 19 million index polygons held in paper format at that time had to be vectorised. The program of vectorisation started in August 2001 and was completed in February 2004.These polygons were mapped against OS Land-Line.
With so many polygons to vectorise within a finite time frame, HM Land Registry was pragmatic in achieving an effective and efficient capture at that time. This meant that we introduced temporary practice, index polygons were completed pictorially and title plans were seldom used to validate an indexed extent.
Index polygons affected by the OS’ Positional Accuracy Programme (PAI) were subsequently amended. HM Land Registry’s PAI program ran from 2005 to 2008.Many were moved in sympathy with the OS mapping. This was done through an automated process. Those that did not meet certain criteria were referred for manual investigation whereby index polygons were manually compared with the title plan.
Around 2009 HM Land Registry embarked on a quality initiative called the Quality Improvement Flowline (QIF); almost 14 million index polygons went through this process. Some minor overlaps were resolved and extent matching was done automatically, each index polygon was reconciled with the title plan. By this time HM Land Registry was taking OS MasterMap (OSMM), the new large scale map product from Ordnance Survey which replaced LandLine.
HM Land Registry receives a daily change only update (COU) of OSMM but this is used for the creation of new Index Polygons and Title Plans, rather than to review or update current registrations. Index Polygons will be updated when there is appropriate activity on a title, or an adjoining title demands a change.
Large scale OS map products (OS Land-Line and OSMM) capture features at various scales 1:1,250 for urban areas, 1:2,500 for semi urban and rural areas and 1:10,000 for mountain and moorland areas.
All HM Land Registry data including index polygons are captured to British National Grid.
6.1 Table 3: NPD feature types
|1||Indicative Extent Current practice||The index polygon is a good representation of, if not identical to the title plan. This is the most common feature in the dataset.|
|2||Footprint Current practice||Capturing indicative extents where multiple registered titles exist in a building result in a cluttered and difficult to interrogate index map. To deal with this, HM Land Registry captures footprint index polygons Footprint indexing involves the capture of an area larger than the title extent. Whilst normally the footprint will be captured to the defined boundaries of a building shown on OSMM. The index polygon should be captured to the smallest footprint that fully accommodates the title extent.
Where the registered title comprises land that falls outside the building footprint for example garden ground or parking space this should be shown as a separate polygon(s) with an indicative extent.
Commonly seen in floor level registrations, also bin stores, advertising hoardings and solar panels.
|3||Artificial Footprint Current practice||Where a large number of floor level registrations affect an unusually large defined area on the OSMM (typically a shopping mall or similar development) indexing to the footprint of the whole development makes interrogating the index map less effective. HM Land Registry mapping system struggles to deal with a huge amount of multiple layered polygons. In such circumstances HM Land Registry may be divide the area into smaller artificial footprint areas within the building footprint.
Additionally if it is difficult to clearly show small registrations that are not defined on the OSMM. We may capture a larger artificial footprint to include all the small areas.
Commonly seen in shopping malls, small plot schemes and bin stores.
|4||Exaggerated Extent Current practice||To allow small areas of land that are undefined on the OSMM to be easily identified all index polygons should have a width of at least 1m. Where a narrow strip of registered land adjoins other registered land, the adjoining index polygon will be reduced in size to allow for the strip to be shown with a 1m width.
Commonly seen with ransom strips and pipelines <1m.
|5||Gridding Former practice||Index polygons were indexed on the appropriate national grid 1km or quadrant sheet. The vectorisation programme was managed by national grid reference. Therefore where index polygons fell across sheets this was replicated. This means that index polygons stopped at sheet joins. The impact of this is that fields, houses, roads for example are sometimes split into parts each with its own PID.|
|Some leasehold index polygons were captured to the extent of the freehold index polygon, even though the extent was lesser than the freehold. HM Land Registry changed this practice because it caused difficulties interrogating the index map to determine title numbers for parts of garden ground and parking spaces.|
Topology is defined as how point, line and polygon features share coincident geometry, in the context of index polygons topology describes how polygons relate to and interact with each other.
Overlaps, gaps, slivers and underlaps all exist in the dataset. Many are genuine and are acceptable but there are some that exist which should not.
|Acceptable overlapping polygons||HM Land Registry deals with registrations at different floor levels, strata, different tenures and classes of title; it is therefore acceptable for polygons to overlap. When overlapping polygons of this nature are referred to the caseworker they classify it accordingly and allow it to remain in the dataset.|
|Illegal overlapping polygons||These are overlaps that arise that shouldn’t be in our data. On system referral of an index polygon overlap, the caseworker investigates and may resolve index polygon overlaps.
However, where title extents genuinely overlap, HM Land Registry has limited powers to amend registered extents so no action is taken until an application to amend/rectify is received.
|Minor overlapping polygons||Overlaps <0.5m2 are not referred to caseworkers for remedial action, this is because they are insignificant and are too small to satisfactorily resolve with the mapping toolset in the mapping system.|
|Gaps, slivers and underlaps between polygons||As part of the registration process consideration is given to adjoining registrations. Where titles are intended to adjoin, practice advices that minor index polygon discrepancies should be resolved.
It is right that some registered titles do not adjoin and in that instance the index polygons will not either
7. Data maintenance
HM Land Registry does not routinely update title plans or index polygons. We may do so in the following circumstances:
- upon receipt of a query received from a customer
- in dealing with an application for registration, HM Land Registry will consider adjoining registrations, after investigation this can give rise to amendments to a title plan and/or index polygon
- when an incorrect index polygon is observed
- some applications, for example sales off from parts of registered titles require the removal of a piece of land from a registered title and the index polygon
Overnight, index polygons created/updated/deleted in the production environment that day are uploaded to the publication environment as ESRI (Environmental Systems Research Institute) shapefiles (PDF). Through this process the polygons undergo simple validation; checking for zero co-ordinate polygons, zero area polygons and duplicate co-ordinate points within polygons. Many of the self-intersections are cleaned for the publication environment and polygons with zero areas and those with an area below 0.1m2 are removed from it.
An index polygon may go through several changes but the change only update (COU) delivery will only contain the latest version. HM Land Registry does not keep the previous versions of it.
NPD is updated monthly.
|Attribute||Data that describes the properties of a feature, for example a point feature may have an attribute describing the point as; a well or a telegraph pole or a tree|
|Class Diagram||A diagram describing the structure and content of a dataset|
|Feature||A data entity, for example a point, line or polygon|
|Feature Catalogue||A document that defines features, often by describing the feature attributes|
|Feature Types||Homogenous collections of common features|
|GIS||Geographic information systems, a combination of information technology hardware and software and trained user that together can capture, analyse and use geographic information|
|Index Polygons||A polygon feature representing the indexed extent of a registered title|
|Index Map||A collection of index polygons to cover a particular area of interest|
|MasterMap||The Ordnance Survey large scale topographic map of the UK|
|Topology||The relationship between geographic features, either within or between layers of information|
9. Data product delivery
9.1 Access to the dataset
There is a charge for the dataset and you will be required to sign a licence.
If you intend to reuse the data within your products and services for commercial gain you must indicate on the Licence and confirm your choice of reuse model.
The Business Development Fulfilment Team can assist in determining your terms of proposed use, such as internal use or permitted reuse.
Should you have any queries about the National Polygon Dataset, please contact the Business Development Fulfilment Team.
9.2 Download package
This package can start at any month of the year, you will be granted access to the Full Dataset, the change only updates and the validation files.
All the files in this package are refreshed and available from the second working day of the stated months.
The data is provided as a CSV file. The format of each file will conform to the following:
- the character used to delimit each field is a comma: ‘ , ’ (ASCII 44)
- all fields will be enclosed within double-quote’s “ “ (ASCII 34)
- when a field is NULL, it will be transmitted as no character between double quotes, i.e. ,” “,
- date fields will be provided in the format DD-MM-YYYY HH:MM:SS For example the date; the fourteenth of December twenty thirteen would be represented as 14-12-2013
- the file will use UTF-8 and ASCII encoding.
- steps will be taken to remove carriage return and line feeds from the data.
- the column heading name will be the first row of the file.
9.3 Naming convention
Please note, if you intend to copy and paste the code below, you must remove any spaces within the text string.
The full file has been split into several files which have a 2GB limit:
Full file LR_POLY_FULL_< 3 character Month > _ < number of file >
Change Only Update file LR_POLY_COU_< DD_MMM_YYYY >
Validation file LR_POLY_VALI_< 3 character Month >
If you want to know more about the National Polygon dataset, please contact us: