OS Terrain 5 ASCII (GIS Sections)

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Ordnance Survey T5 Data in ASC — OS Terrain 5 in ASCII with optional Contours | © Crown copyright and database rights 2025 OS AC0000848283

Ordnance Survey T5 ASCII (DTM grid) - Optional 5m Contour Lines in SHP, GPKG or GML

Q: What is OS Terrain Chunks for GIS users?

OS Terrain Chunks is a detailed Digital Terrain Model (DTM) product derived from Ordnance Survey’s Terrain® 5 dataset. It provides highly accurate elevation data at 5-metre resolution, ideal for integration into GIS workflows. Unlike purchasing full OS tiles (also available on our OS Terrain 5m Grid & Contours Tiles page), OS Terrain Chunks allow you to precisely trim, cut, and rotate data to fit your specific GIS or project location—perfect for smaller or bespoke projects without the need for full-tile purchases.

Q: How frequently is OS Terrain GIS data updated?

The OS Terrain dataset is updated quarterly (January, April, July, October), ensuring your GIS projects always have access to current and accurate elevation and contour information for precise environmental modelling, planning, and visualisation.

Q: What applications is OS Terrain GIS suitable for?

OS Terrain GIS data is ideal for 3D terrain visualisation, flood-risk assessment and hydrological modelling, line-of-sight and signal propagation studies, wind-farm location planning, and landscape and environmental impact assessments. This reliable digital terrain model greatly reduces the need for extensive field surveys.

Q: What's the difference between a DEM and a DTM in GIS?

A Digital Elevation Model (DEM) generally refers to raster elevation datasets representing the surface elevation, which can include both natural and man-made features like buildings and vegetation. A Digital Terrain Model (DTM) specifically represents the bare-earth terrain. DTMs have had man-made structures, vegetation, and other surface features digitally removed, providing a clean elevation model of the natural landscape. In short, a DEM can include surface features, while a DTM strictly represents natural terrain elevations.

OS Digital T5 ASCII - Sections/Data Chunks - Overview

On this page, we offer smaller sections than the standard OS Terrain 5 supply of 5km x 5km tiles, ideal for users seeking more compact portions of Terrain 5 data for their project.

OS Terrain refers to Ordnance Survey’s digital height products, designed to provide precise three-dimensional digital terrain models (DTMs) covering Great Britain. A DTM accurately represents the earth's surface by excluding features such as buildings, vegetation, and other structures that rise above ground level.

Designed for GIS users
OS Terrain 5 is a mid-resolution DTM specifically engineered for integration with large-scale mapping data
Starting from 100m x 100m - ideal for smaller areas of interest
OS Terrain 5 is delivered in forms—grid (ASCII) format
Within your GIS setup you can generate contours from the ASC data at any contour interval required

Alternative Products:

OS Terrain 5 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
Environmental analysis
Line of sight planning
Viewshed modelling
Landscape visualisation and fly-through sequences
Planning and development
Signal propagation
Wind farm location planning
Flood risk assessment
Foundation for 3D modelling
Optional OS Mastermap base mapping to match your selection

For larger areas:

Downloadable Samples

Key Documents:

QGIS Supporter:

Product:	OS Terrain® 5 -ASCII
Base Mapping	None included as default BUT option to add OS MasterMap Topography Layer®
Scale	Any within a GIS setup
Coverage	Full Great Britain coverage (sorry this excludes Northern Ireland - try OSNI)
Format	ASCII DTM for GIS users
Software Required	GIS (Geographic Information System) - Advanced software
Product Price	From: £12.50 + vat
Delivery Method	Email
Turnaround Time	Email: Target time of 30 mins (7 days a week 7am to 11pm) - Larger files may take longer to generate
Currency	Current - Latest available direct from Ordnance Survey
Samples	Click here to download sample - ASCII DTM Layer Only \| ASCII Click here to download sample - Contours \| SHP Click here to download sample - Contours \| GML
Key Features	Text-based, simple file format Easily imported into GIS software Compatible with diverse analysis tools Suitable for terrain modelling and hill shading Geo-referenced
Uses	ASCII DTM/DEM data is widely used for GIS, hydrological modeling, landscape analysis, urban planning, archaeology, environmental simulations, and agriculture management
Number of Printouts	Unlimited outputs from GIS within the selected licence term (1, 2 or 3 years)
3D Modeling	DTM like OS Terrain 5 is ideal for creating hill shading in QGIS, enabling visual enhancement of terrain features and landscape relief.
Info	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) \| Contour data is available in GML 3.2.1, and Esri shapefile or GeoPackage
GIS Tiles	We also supply OS Terrain 5 in the OS standard supply of 5km x 5km GIS tiles - click to visit
Licence Term	Please go to the Licence tab below
Accuracy	OS Statement: OS Terrain 5 has been measured against with GPS points in a range of sample areas to provide a root mean square error (RMSE) value for the height points in each geographic area; urban and major communication routes, rural, and mountain and moorland. Urban and major communication routes = 1.5 metres RMSE* Rural = 2.5 metres RMSE Mountain and moorland = 2.5 metres RMSE * Root mean square error. This is the average of the mean heights collected in a sample area. The contours are generated from the OS Terrain® 5 using a third party application. They are not subject to Ordnance Surveys accuracy / specifications and are designed to provide a 2 dimensional guideline only.
Further Reading	OS Terrain 5 User Guide \| OS Doc

Item	Permitted	Alternative Product / Notes
GIS Use		For larger areas we would recommend using Shapefile Contours \| GML Contours \| ASCII Grid 5km x 5km Tiles - click to visit
Ready for CAD		A more suitable product in DXF or DWG: - click to visit
Printing Extra Copies		Unlimited outputs/scales from your software within the licence term
Permit your Contractors to use the purchased Licensed Data		Contractor Form Below - Best Practice: Make sure you select the relevant number of users/terminals if using a contractor before purchase

FREQUENTLY ASKED QUESTIONS

What is OS Terrain Chunks for GIS users?

OS Terrain Chunks is a detailed Digital Terrain Model (DTM) product derived from Ordnance Survey’s Terrain® 5 dataset. It provides highly accurate elevation data at 5-metre resolution, ideal for integration into GIS workflows.
Unlike purchasing full OS tiles (also available on our OS Terrain 5m Grid & Contours Tiles page), OS Terrain Chunks allow you to precisely trim, cut, and rotate data to fit your specific GIS or project location—perfect for smaller or bespoke projects without the need for full-tile purchases.

How frequently is OS Terrain GIS data updated?

The OS Terrain dataset is updated quarterly (January, April, July, October), ensuring your GIS projects always have access to current and accurate elevation and contour information for precise environmental modelling, planning, and visualisation.

What applications is OS Terrain GIS suitable for?

OS Terrain GIS data is ideal for:

3D terrain visualisation
Flood-risk assessment and hydrological modelling
Line-of-sight and signal propagation studies
Wind-farm location planning
Landscape and environmental impact assessments
This reliable digital terrain model greatly reduces the need for extensive field surveys.

Do I need an Ordnance Survey licence to use OS Terrain GIS data?

No, you do not require your own OS licence. As an authorised OS Premium Partner, UK Map Centre supplies OS Terrain GIS data under an Internal Business Use (IBU) licence included with your data. This IBU licence permits unlimited internal printing, export, and analysis within your licensed period.
However, if you require extended use—such as external publishing, commercial applications, or online distribution—Ordnance Survey offers additional bolt-on licences. For further details, please visit Ordnance Survey’s official licensing page.

What's the difference between a DEM and a DTM in GIS?

Digital Elevation Model (DEM) generally refers to raster elevation datasets representing the surface elevation, which can include both natural and man-made features like buildings and vegetation.

Digital Terrain Model (DTM) specifically represents the bare-earth terrain. DTMs have had man-made structures, vegetation, and other surface features digitally removed, providing a clean elevation model of the natural landscape.

In short, a DEM can include surface features, while a DTM strictly represents natural terrain elevations.

Trusted GIS Base Mapping from Ordnance Survey Experts.