Users should note that the data is not intended to be used as definitive but indicative. Users are encouraged to use the data "as is" and not to further edit the data. Feedback on interpretational issues is always welcomed.
The paper map provided at the time of designation is the official map.

Digital boundary data is not definitive and should be used as indicative.

Digital boundaries are normally aligned to the position of relevant features as mapped on the primary mapping source (OS MasterMap) and are subject to continual revision.

Almost all of the original designation maps used a different map - often the Ordnance Survey 1:10560 or 1:10000 map - for background context, therefore the digital boundary may not have a geometrical match with the boundary on the designation documents, but will refer to the same features on the ground.

Please note the initial release of SuperSite data (April 2004) contains a small number of known data errors which will be corrected over time. Also, the geometry of the SAC, SPA and Ramsar site data will differ from that available from the JNCC web site until such time as the SuperSite data replaces the JNCC data.

The boundary defines the extent of the area of the Theme.

There may be excluded areas within the Theme boundary.

The Theme boundary may follow, or be "mered", a feature mapped on the primary source, such as a hedge or stream, or it may be "undefined". It may follow a feature which is liable to change, for example, the Mean Low Water mark.

The data normally provided does not carry an attribute describing the source feature. This "capture" information may be provided for small extents of boundary on demand.

This section describes the method of data capture and maintenance and is included for technical information - for details of the actual data provided please see later sections.

The boundary data is maintained as "Lines" and "Pins".

The boundary geometry for each Theme is captured as a series of connecting "Lines" using OS MasterMap as a primary reference or source.

Theme boundary features that are mered exactly to features on OS MasterMap are cloned (copied) and will share OS MasterMap geometry, and if not mered, are captured using a variety of other source material.

Every section of line will be assigned a "capture code" (please note that this code is not included in the polygon data provided with this document.)

Where two or more Themes share a boundary features, the geometry will be captured once.

Lines have no Theme attributes - these are held within the "Pin" attributes.

The end nodes or vertices of every Line will always join exactly with the end node of another.

The Lines that together describe a self contained area of land - which describe part of a Theme or an excluded area - are referred to as a "Collection of Lines".

A Collection of Lines that describes one or more Themes will have one or more "Pins" placed within the containing Lines.

A Pin is a point object.

The Pin will have an attribute describing the Theme and a unique integer number, known as the "Theme ID" or "ThemeID" which in turn will refer to further information about the particular "Thing" described by the Collection of Lines.

For example, the ThemeID for "The Quantocks" SSSI is 1001391.

The Lines and Pins data is stored in a spatial database (currently Oracle Spatial) from which draft and final data is produced using a variety of software tools.

All data is captured to the Ordnance Survey National Grid sometimes called the British National Grid.

OS MasterMap - produced and supplied by Ordnance Survey from data at 1:1250, 1:2500 and 1:10000 surveying and mapping standards - is used as the primary source. See http://www.ordnancesurvey.co.uk/oswebsite/products/osmastermap/ for more information

Other sources - acquired internally and from external suppliers - may include aerial imagery at resolutions ranging from 25cm to 2m, Ordnance Survey 1:10000 raster images, historical OS mapping, charts and chart data from UK Hydrographic Office and other sources, scanned images of paper designation mapping (mostly originally produced at 1:10560 or 1:10000 scales), GPS and other surveyed data, and absolute coordinates.

Users should note that use of the data, for mapping, or in a GIS, with reference mapping other than OS MasterMap, may give ambiguous results.

The accuracy of the data will, in general, match that of the primary source material, OS MasterMap.

Natural England received a complete set of OS MasterMap data extracted on 8 August 2002. No further updates have been applied.

The data is intended to provide internal and external users with a ready-to-run set of boundary data with no further editing required by the user. A range of quality assurance checks are made throughout the data capture process.

Data capture is carried out according to the SuperSite Rule Book using controlled environments to ensure correct interpretation and connectivity.

Quality assurance tools may be interactive, semi-automatic and automatic as appropriate.

The data is normally provided free of charge and can be used freely by users in their normal internal business. The only current restriction is to offer the data for sale, that is, the onward provision of the data as supplied or after manipulation by the user, as part of a data package or software application. The current conditions of usage are explained in Licence.doc which is provided as part of the data package. Contact us if you have any queries.

The data is made available as polygons in GIS files based on Themes.

The polygons will be supplied with a nominal colour symbology which users may wish to use.

Each "Thing" will have one or more polygons, and where two or more, these will be combined as one object.

Each object will have a set of attributes (see below).

Polygons are normally provided as an England-wide dataset - one per Theme - but may also be split into convenient "chunks" of data, for example, 100km, in which case, any polygons straddling the cutting device will be provided in adjoining "chunks". This is the "hairy chunk" similar in concept to the supply of OS MasterMap. Therefore users must note the possible need for removal of duplicates before use.

All data is supplied as Zip Files - compressed using WinZip - for more efficient delivery via Internet/Email.

Each Zip file will contain the appropriate graphics data plus other supporting text data.

Data is currently provided in several GIS formats:

• MapInfo TAB
• MapInfo MIF/MID
• ESRI Shape
• AutoCAD DXF (geometry only)

Best explained by using the SSSI Theme as an example...