Every terrain map, every flood model, every viewshed analysis and every hillshade starts with the same thing: a digital elevation model, a raster where each pixel holds the height of the ground. The good news is that you can download high-quality elevation data for almost anywhere on Earth, for free, from government programmes that have already mapped the planet. This guide covers the best free DEM sources in 2026, how they differ, and how to use them in QGIS.

SRTM: The Classic 30-Metre Global DEM

The Shuttle Radar Topography Mission, flown by NASA in 2000, mapped the Earth's land surface between 60 degrees north and 56 degrees south at 30 metre resolution, and its data is free for everyone. SRTM is the workhorse of global elevation data: it is consistent, well documented, and available for almost every land area on Earth except the high Arctic. Download it from USGS EarthExplorer, NASA Earthdata Search or the OpenTopography portal, choosing the SRTM 1 arc-second product for the 30 metre version. Its limits are real: it is a surface model in many places, meaning it includes tree canopy and buildings rather than bare earth, and it has voids in steep mountain terrain where the radar shadowed itself. For regional work, watershed analysis and general terrain visualisation, it is still the first DEM to reach for.

Copernicus GLO-30: The Modern Replacement

The Copernicus GLO-30 DEM, built from TanDEM-X radar data by the European Space Agency, is the best free global DEM available in 2026. It covers the whole planet at 30 metre resolution, including the high latitudes SRTM misses, and it is a true digital elevation model with better vertical accuracy than SRTM in most terrain. Download it from the Copernicus Data Space Ecosystem or the OpenTopography portal, which also offers the 90 metre GLO-90 version for faster downloads. For most new projects, GLO-30 is the better default: it is newer, it covers more of the planet, and its accuracy is measurably better. Keep SRTM in mind only when you need to compare against old work that used it, or when you need its specific void-filled version for a particular region.

ALOS, ASTER and National Datasets

Two more global sources are worth knowing. The ALOS World 3D 30-metre DEM, from the Japan Aerospace Exploration Agency, is built from optical stereo imagery and is often the best choice in steep mountain terrain where radar struggles. ASTER GDEM, from NASA and Japan, is the oldest of the global optical DEMs and has known artefacts, but it is still useful as a cross-check. Beyond the global products, national datasets are almost always better where they exist: the USGS 3DEP programme provides 1-metre and 10-metre LiDAR-derived elevation for much of the United States, the Environment Agency publishes free LiDAR elevation for England at up to 1 metre, and many European countries publish similar open data. Always check for a national dataset before downloading a global one: a 1-metre national DEM will beat a 30-metre global DEM every time.

Using a DEM in QGIS

Download the DEM as a GeoTIFF and drag it into QGIS. The first thing to do is style it: a hillshade, under Raster, Analysis, Hillshade, or the Layer Properties Symbology tab with a singleband pseudocolor ramp, turns a grey raster into a readable terrain map instantly. From a DEM you can derive slope, aspect and contours, all under the Raster menu or the Processing Toolbox, and you can run a viewshed analysis to see what is visible from a viewpoint, or a watershed analysis to delineate drainage basins. Check the coordinate system before you do any analysis: a DEM in geographic coordinates, degrees, will give wrong slope and distance values, so reproject to a projected system such as the local UTM zone first. And check the vertical datum: some DEMs use the EGM96 geoid and others use the WGS84 ellipsoid, and the difference can be tens of metres, which matters for flood modelling.

Which DEM Should You Download?

For a global project or a quick regional analysis, download Copernicus GLO-30: it is the best free global DEM in 2026. For the United States or England, check the national LiDAR-derived data first, because the resolution is far better. For steep mountains, try ALOS World 3D as a comparison. For historical comparison, use SRTM. Download the smallest tile that covers your area, clip it to your study boundary to keep file sizes manageable, and always keep a note of which DEM you used and its resolution, because a flood model built on a 30-metre DEM and a flood model built on a 1-metre DEM will give very different answers. The data is free, the software is free, and the terrain of the entire planet is waiting in a GeoTIFF.