OS Terrain 50 Overview

OS Terrain is the name given to Ordnance Survey’s height products. The two products available, OS Terrain 5 and OS Terrain 50, provide detailed three-dimensional digital terrain models (DTMs) of Great Britain. A DTM primarily defines the ground surface, having removed all protruding features (such as buildings and trees) elevated above the bare earth. The main difference between the two products is their level of resolution:

• OS Terrain 5 is a mid-resolution DTM, designed to be interoperable with our large-scale data.

• OS Terrain 50 is a lower-resolution DTM product, designed for landscape visualisation and analysis over large areas. It is an Open Data product and, as such, it is free to view, download and use for commercial, educational and personal purposes.

OS Terrain 50 is published as both grid data and contour data in a variety of formats. Both data types are created from the same source data and are supplied as 10km-by-10km tiles. These tiles are identified by quoting the National Grid reference of the south-west corner of the area they cover.

• OS Terrain 50 grid: A grid of heighted points with regular 50m post spacing.

• OS Terrain 50 contours: A contour dataset of 10m interval standard contour polylines. This includes mean high water and mean low water boundaries and spot heights.

Key features of the product

• The product is maintained by our integrated 3 to 5-year flying programme and is synchronised with our other product updates.

• There is specific modelling of significant features, particularly networks.

• DTM grid data is available in ASCII (American Standard Code for Information Interchange) grid and Geography Markup Language (GML) 3.2.1, using Open Geospatial Consortium (OGC) Simple Features Profile (level 0).

• DTM contour data is available in GML 3.2.1, Esri shapefile, GeoPackage and vector tiles (MBTiles).

• There is full coverage of Great Britain.

• It is provided free at the point of use as a download through the Ordnance Survey Data Hub.

• It is designed to work with Ordnance Survey’s small-scale data.

• The product is updated annually in July.

• It is based on the INSPIRE elevation specification.

Product applications

OS Terrain 50 provides an ideal base to enable the third dimension for other data within an appropriate geographical information system (GIS). The height data has been created from a source that is also used to update our large-scale data products.

OS Terrain 50 can be used in conjunction with various Ordnance Survey digital products for analytical, modelling, planning and visual purposes. These uses enable customers to undertake the following:

• Asset/site management

• Signal propagation

• Environmental analysis

• High-level development

• Geological analysis

• Line of sight planning

• Viewshed modelling

• Using the product as a visual aid

Accuracy

OS Terrain 50 has been compared with GPS points in a range of sample areas to provide a route mean square error (RMSE) value for the height points in each geographic area: urban and major communication routes, rural, and mountain and moorland. OS Terrain 50 grid data has been verified to be 4m RMSE.

INSPIRE compliance

OS Terrain 50 is designed to be INSPIRE (Infrastructure for Spatial Data in Europe) ready. Ordnance Survey is a leading member of the UK Location Programme, which is charged with delivering INSPIRE, a directive that applies to all member states and aims to enable more joined-up data across public bodies for environmental applications.

At the time of OS Terrain's product development, the INSPIRE elevation specification had not been finalised. The data structures of OS Terrain products and the details of the GML encoding have been based on the draft INSPIRE specification.

For more information about INSPIRE and UK Location, please view the INSPIRE webpages.