Free DEM Data: Where to Download Elevation Models and What to Check
Free elevation data comes in two very different kinds. Global models cover almost every land area at about 30 metres and were measured from space, so they describe the top of the surface — forest canopy and buildings included. National lidar programmes cover single countries at a metre or better and usually deliver bare-earth terrain. Which one fits depends on the job, and on three checks people often skip: surface or terrain, vertical datum, and licence.
Global elevation models (about 30 m)
Copernicus DEM GLO-30 is a global surface model on a 1 arc-second grid (about 30 m), made from TanDEM-X radar data acquired between 2011 and 2015. Heights refer to the EGM2008 geoid, and the 30 m and 90 m versions are available worldwide under a free licence.
SRTM 1 arc-second (SRTMGL1) comes from the February 2000 Space Shuttle radar mission and covers land between 60° N and 56° S, with heights in metres above the EGM96 geoid; its voids were filled from other datasets. NASADEM is a reprocessing of the same SRTM data with improved void filling and a geoid reference. AW3D30 is a 1 arc-second surface model from the optical PRISM sensor on the ALOS satellite, free for commercial and non-commercial use after registration. ASTER GDEM version 3 extends coverage to 83° N and 83° S on the EGM96 geoid, though its own documentation warns that anomalies and artifacts remain.
National lidar programmes (1 m and finer)
Where a national programme exists, it is usually the better starting point. In the United States, the USGS 3D Elevation Program publishes bare-earth DEMs — 1 m where lidar has been flown, and 1/3 arc-second seamless coverage of the whole country — free of charge and without use restrictions, typically referenced to NAVD88. In England, the Environment Agency's LIDAR Composite DTM covers about 99% of the country at 1 m under the Open Government Licence, referenced to Ordnance Datum Newlyn, built from surveys with a stated vertical accuracy of ±15 cm RMSE.
Many other countries publish lidar-derived terrain through their mapping agencies, and portals such as OpenTopography host global models alongside country-wide datasets. Prefer the agency's own download page: it states the datum, the accuracy and the licence.
Surface or terrain? The first check
Copernicus DEM and AW3D30 are surface models: in a forest they report the canopy, in a city the rooftops. SRTM and ASTER, measured from above by radar and by stereo imagery, are affected by vegetation and buildings in the same way. That is fine for regional relief, landscape-scale line of sight or a first look at a site, and wrong for anything that needs the ground — earthwork quantities, drainage on vegetated slopes, design levels.
Lidar DTMs remove vegetation and buildings; the USGS defines bare-earth data as terrain free from vegetation, buildings and other man-made structures.
| Dataset | Coverage | Grid | What it describes | Heights relative to | Licence |
|---|---|---|---|---|---|
| Copernicus DEM GLO-30 | Global | 1 arc-second (≈30 m) | Surface model (radar) | EGM2008 geoid | Free licence, worldwide |
| SRTM 1 arc-second | 60° N – 56° S | 1 arc-second (≈30 m) | Surface (radar, 2000) | EGM96 geoid | Open, without restriction |
| NASADEM | 60° N – 56° S | 1 arc-second (≈30 m) | Reprocessed SRTM | Geoid | NASA open data |
| AW3D30 | Global land | 1 arc-second (≈30 m) | Surface model (optical) | Height above sea level | Free after registration, JAXA terms |
| ASTER GDEM v3 | 83° N – 83° S | 1 arc-second (≈30 m) | Surface (optical stereo) | EGM96 geoid | Free, provided as is |
| USGS 3DEP | United States | 1 m (lidar areas), 1/3 arc-second seamless | Bare earth | Typically NAVD88 | Free, no use restrictions |
| England LIDAR Composite DTM | ≈99% of England | 1 m | Bare earth | Ordnance Datum Newlyn | Open Government Licence |
Vertical datum: the second check
Global models give heights above a geoid — EGM2008 for Copernicus DEM, EGM96 for SRTM and ASTER GDEM — while GNSS surveys and many drone DEMs give heights above the ellipsoid, and national datasets use their own datum, such as NAVD88 in the United States or Ordnance Datum Newlyn in England. The differences reach tens of metres. Before comparing a free DEM with your own survey, bring both to the same vertical reference; a geoid grid does the conversion.
Resolution is not accuracy
A 30 m grid spacing says how often a height is stored, not how right it is. A global model smooths a stockpile, a bench or a road cutting into its cells, and its vertical errors are measured in metres rather than centimetres. Use global data for context, planning and regional analysis; use a drone survey or a lidar DTM for quantities.
Licences
Free does not always mean unconditional. SRTM is shared without restriction, 3DEP products carry no use restrictions, England's composite DTM is under the Open Government Licence, AW3D30 is free under JAXA's terms of use after registration, and Copernicus DEM is released under its own free licence. Read the terms and keep the attribution each licence asks for.
Opening free DEM data in STREAM
Global tiles and the arc-second 3DEP products are delivered in geographic coordinates (latitude and longitude). Reproject them to the projected coordinate system of your project — for example the local UTM zone — before loading, so that distances, areas and volumes are measured in metres. Download GeoTIFF where the portal offers it.
Several tiles of the same area load as one surface: STREAM binds visible DEMs into a single mosaic, so analysis, contours and cross-sections read across tile edges. Vertical Reference converts the heights with a geoid grid (GTX, GeoTIFF, GRI or BYN) into a new GeoTIFF and leaves the download untouched.
Frequently asked questions
Where can I download free DEM data?
Global models — Copernicus DEM, SRTM, NASADEM, AW3D30 and ASTER GDEM — cover almost all land at about 30 m. National lidar programmes, such as USGS 3DEP in the United States and the Environment Agency's LIDAR Composite DTM in England, cover single countries at 1 m or finer.
Are free global DEMs bare earth?
No. Copernicus DEM and AW3D30 are surface models that include vegetation and buildings, and SRTM and ASTER are affected by them in the same way. For bare-earth terrain, use a national lidar DTM where one exists.
What vertical datum do free DEMs use?
It varies: Copernicus DEM uses the EGM2008 geoid, SRTM and ASTER GDEM use EGM96, and national datasets use their own datum, such as NAVD88 in the United States or Ordnance Datum Newlyn in England. Bring both datasets to the same reference before comparing them with a survey.
Can I use free DEM data for earthwork volumes?
Not for quantities. A 30 m global model smooths stockpiles, benches and cuttings into its cells, and its vertical errors are measured in metres. Use it for context and planning, and a drone survey or a lidar DTM for volumes.
Can STREAM open free DEM data?
Yes. Reproject the tiles to your project's projected coordinate system and load them — several tiles of the same area become one surface — then convert the vertical reference with a geoid grid if it differs from your survey.
Sources
- Copernicus Data Space — Copernicus DEM collection
- NASA Earthdata — SRTM Global 1 arc second (SRTMGL1) V003
- NASA LP DAAC — SRTM Collection User Guide (V3)
- NASA Earthdata — NASADEM
- JAXA EORC — ALOS World 3D 30m (AW3D30)
- NASA Earthdata — ASTER Global DEM V003
- USGS — About 3DEP Products & Services
- USGS — Projection, datums and resolution of 3DEP standard DEMs
- data.gov.uk — LIDAR Composite Digital Terrain Model (DTM) 1m
- OpenTopography
Open and analyse large DEMs in STREAM
Native Windows · fully offline · free beta