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OS MasterMap® Topography Layer technical information

Specification

OS MasterMap® Topography Layer

Coverage

Great Britain (England, Scotland and Wales)

Availability

Order by:

  • Great Britain
  • England
  • Scotland Wales
  • User-defined areas:
  • specific identities of National Grid tiles;
  • administrative region;
  • Government Office Region;
  • bounding box; or
  • irregular shape drawn within the service using the tools provided or imported into the service.

Data source

Ordnance Survey’s OS MasterMap Topography Layer is sourced directly from data captured by air and ground survey techniques. The dataset is maintained as a continual process subject to capture policy based on the type of features and their location. The date of creation or change of a feature and the nature of change are given in data supplied in GML as attributes against polygons, lines and points.

Data structure

Vector point and line and polygon structure.

Scale

The OS MasterMap Topography Layer data is suitable for viewing as follows:

For urban areas the data has been captured and maintained at a base scale of 1:1250 and is cartographically suitable for display at this scale.

For rural areas the data has been captured and maintained at a base scale of 1:2500 and is cartographically suitable for display at this scale.

For remote (mountain and moorland) areas the data has been captured and maintained at a base scale of 1:10 000 and is cartographically suitable for display at this scale.

Transfer format

GML 2.1.2

Storage volumes

Complete national supply is approximately 38 Gb in zipped GML file format.

Supply media

CD, DVD and FTP (for orders under 400 Mb)

Coordinate precision

The coordinates in OS MasterMap data are stored at a greater precision than a decimetre. The coordinates in the OS MasterMap Topography Layer data are capable of holding values to millimetre precision, although in most instances the values are given to centimetre precision (for example, 491308.950).

Update interval

Complete resupply is available.

Change-only update is available every six weeks.

OS MasterMap service enables users to place regular scheduled orders, subscribe to the Managed Great Britain sets (MGBS) service, which gives full supply and updates for the whole of Great Britain, or place ad hoc orders as required.

Styling

A default style set and the mapping of features to these styles are provided as XML files on the website at

http://www.ordnancesurvey.co.uk/oswebsite/xml/schema/index.html

and within the user guide in the technical specification section, annexe C. The style set defines standard polygon fills, line styles and point symbol definitions, allowing a common appearance of the data across software systems to be achieved.

Geometry types

Polygons

Lines

Points 

Annotations (text).

Coordinate reference system

British National Grid (OSGB36®)

Unique identifier

Unique IDs (TOIDs) are provided for each feature.

 

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