Ordnance Survey T5 ASCII (DTM grid) with Optional 5m Contour Lines - Email delivery in 20 minutes

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 Height Layer Sections in GIS format SHP | GPKG or GML

Ordnance Survey Premium Licenced Partner • GIS Compatible Height layer • Optional Contours Available

Address

Placename

Grid

W3Words

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QGIS screenshot showing OS Terrain 5 ASCII data with yellow and green 5-metre contour lines generated using QGIS contouring tools overlaid on dark coastal terrain

3D hillshade terrain render in golden and brown tones showing mountain valleys, lochs in blue, and sharp ridgelines created from ASCII grid data

Greyscale hillshade and shaded relief rendering showing mountain terrain, ridgelines and valleys in subtle grey tones derived from OS Terrain 5

Artistic macro photograph of a physical terrain model with brown contour lines carved into the surface showing elevation detail at close range

3D terrain render showing green and brown mountain valleys with river valley, steep ridges and topographic detail created in GIS software

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QGIS workflow: ASCII data loaded and 5-metre contours generated using QGIS contouring tools - fine control over contour intervals. 3D hillshade render from OS Terrain 5 sections - lochs, valleys and ridge patterns visualised in 3D terrain software. Greyscale shaded relief - subtle hillshade revealing elevation detail across mountain and valley terrain. Physical terrain model with carved contour lines - the raw height grid translated into tactile form for landscape understanding. 3D terrain surface showing valley and river networks - green and brown elevation rendering in GIS environment.

OS Terrain 5 ASCII Sections

Custom rectangle - your area of interest
ASCII grid (.asc) format
5-metre grid spacing
Heights in metres above ODN
No contours - generate your own in GIS
Starting from 100m x 100m
One file per section
Updated quarterly

Sample Download ↓ OS Tech Spec ↗

OS Terrain 5 ASCII Grid Sections - Height Data Trimmed to Your Site

OS Terrain 5 sections deliver a custom rectangle of raw ASCII (.asc) height grid data trimmed to your area of interest - unlike fixed 5 km x 5 km tiles that force you to buy unused coverage. Each section is a single file containing elevation posts on a 5-metre grid, with heights in metres above Ordnance Datum Newlyn (ODN), georeferenced to the British National Grid (EPSG:27700).

The ASCII format is universal - import it directly into QGIS, ArcGIS, Global Mapper, Mapnik or any GIS software that reads .asc raster grids. No contours are supplied with the data - instead, you generate contour lines at whatever interval you need using your GIS software. In QGIS, for example, you can create contours at 0.5 m, 1 m, 2 m, 5 m or any custom interval from the underlying 5-metre grid. That flexibility means one download serves multiple project needs.

Frame your area on the interactive map, choose your rectangle size, pay online and the ASCII grid file is emailed to you in around 30 minutes. Updated quarterly (January, April, July, October) so your elevation data always reflects the latest OS survey revisions.

What Is an OS Terrain 5 ASCII Section?

An ASCII section is a single, custom-sized rectangular file clipped to your area of interest. Unlike the fixed 5 km x 5 km tile product, there are no tile boundaries or overlaps - just your site, trimmed cleanly to size. The file contains raw elevation data arranged on a 5-metre grid, readable by any GIS package that supports ASC/ArcGrid format.

Pay Only for What You Need

Define your rectangle and buy exactly that footprint - from 100 m x 100 m up to the full GB extents. No wasted coverage, no tile overlap charges, no minimum purchase of multiple 5 km tiles. Smaller sites mean smaller files and faster downloads.

Generate Contours at Any Interval

The raw 5-metre grid is your starting point. In QGIS, ArcGIS or Global Mapper, use the built-in contouring tools to generate contour lines at 0.5 m, 1 m, 2 m, 5 m or any custom interval you choose - no need to buy different contour products for different project phases or uses.

One File No Tile Boundaries

A single seamless ASCII grid clipped to your boundary - no seaming between tiles, no overlapping coverage, no confusion about which tile covers which part of your site. Import it once and your entire study area is ready for analysis.

Unlimited GIS Outputs Under Licence

Once downloaded, you can generate contours, hillshades, aspect grids, slope maps, viewsheds and any other GIS analysis from the raw height data under your OS licence. One purchase unlocks multiple analytical outputs from the same underlying dataset.

Updated quarterly - OS Terrain 5 is refreshed every three months (January, April, July, October), so your elevation data reflects the latest survey revisions across Great Britain.

Not a GIS User?

If you work in CAD (AutoCAD, Civil 3D, BricsCAD) and want height data ready to use with pre-generated contour lines, see our OS Terrain 5 DTM for CAD product. We convert the raw grid into DWG and DXF format with contours at your chosen interval, so you can open the file and start working immediately without any GIS tools.

When Do I Need OS Terrain 5 ASCII Sections?

ASCII sections are designed for GIS professionals and technical analysts who need raw elevation data to drive their own spatial analysis workflows. Common uses include:

Flood Risk Modelling

Use the ASCII grid to model water flow paths, inundation extents and flood hazard zones in HEC-RAS, MIKE FLOOD or bespoke hydrological models. Raw height data with no pre-processed contours gives you control over the analytical workflow.

Drainage & Earthworks Design

Generate contours at 0.5 m or 1 m intervals for detailed site grading plans, cut-and-fill analysis, drainage network design and subsurface utility routing. The 5-metre grid captures sufficient detail for sub-metre earthworks calculations.

Slope Stability & Geotechnical Assessment

Calculate slope angle, aspect and upslope contributing area from the raw grid - inputs for slope stability analysis, landslide susceptibility mapping and geotechnical site characterisation in ArcGIS or QGIS.

Viewshed & Line of Sight Analysis

Model intervisibility, assess visual impact from proposed structures, plan utility corridors and evaluate landscape character using standard GIS viewshed tools built on the ASCII grid.

Wind Farm & Renewable Energy Siting

Assess wind exposure, plan solar panel orientation and evaluate terrain-based energy generation potential using topographic analysis of the raw height grid.

3D Visualisation & Fly-Through

Load the ASCII grid into 3D software (Blender, SketchUp, CityEngine) to create terrain models, animated fly-throughs and immersive landscape visualisations for design review and client communication.

Environmental Impact Assessment

Support EIA workflows with baseline terrain analysis - habitat suitability modelling, species movement corridors, surface water catchments and landscape character assessment built from accurate elevation data.

Landscape Architecture & Grading

Generate contours at your chosen interval and overlay them onto landscape masterplans for grading design, planting arrangement and hard landscaping layout that respects site topography.

About UK Map Centre LLP

UKMapCentre.com is a sustaining member of QGIS — QGIS Supporter

UKMapCentre.com is a member of The Association for Geographic Information — AGI Member

Alternative Products

OS Terrain 5 Tiles - 5km x 5km with Contours OS Terrain 5 for CAD - DWG/DXF with Contours OS MasterMap for GIS 3D OS MasterMap - DTM, Buildings & Aerial

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 Overview

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.