Terrain — how this layer is made

What you are looking at

The colour of the map shows the height of the land above sea level. Shading represents the shape of the ground, so your brain can correctly interpret ridges and valleys. There are no points to click. This map is a value at every pixel rather than a set of places.

Where the data comes from

Every height here was measured by radar from orbit. The Copernicus DEM GLO-30 dataset comes from the German Aerospace Centre's TanDEM-X mission, which flew two satellites in close formation and read the shape of the ground from the difference between their two returns. We do not model or estimate anything ourselves. The samples sit about 30 metres apart, and Copernicus quotes a vertical error better than 4 metres over most of the world.

Colour

The colour represents height, so don't read anything else into it. The Sahara is green where it is low, and it is sand. The Congo basin is green because it lies near sea level rather than because it is forested, and Tibet is brown because it is high.

Land below sea level is pink in all four schemes, because how low the ground lies is a fact about it rather than a choice of palette. The deeper the pink, the lower the ground: pale for the Dutch polders and the Fens, which sit a few metres down, and deep magenta for the shore of the Dead Sea at about 430 metres below the sea.

You can choose between four schemes in Settings, and the class breaks never change, so the same height is always the same step. Atlas is the default, green through tan to brown with pale summits, and it suits big landscape such as the western Alps. Slate drops colour altogether, which may suit you if you find green against brown hard to separate. Bands repeats one short sequence between each pair of levels, so gentle country shows a full run of colour. Its colour is then no longer a height. Relief keeps the atlas colours and deepens the shading.

It measures the top of things

This is a surface model. The height recorded is the top of whatever the radar hit, which over forest is the canopy and over a city is the rooflines. In closed-canopy rainforest that reaches thirty metres or more. A wooded valley and a bare one of the same true depth would produce different results here. One open dataset corrects exactly this, FABDEM, and its licence rules it out for us.

The shading is drawn in your browser

The light and shade are not pre-made pictures. The tiles carry a height per pixel, and your browser reads the slope between neighbouring pixels and lights it as you pan. The contour lines work the same way, traced live from the same tiles, so nothing extra is downloaded for them, and from zoom 10 every line carries its own height rather than every fifth one. You can move the sun with the dial to change the angle of the sun and therefore the shading angle, because whether a shaded hill reads as a hill or as a hollow is based on your visual perception.

Which year

The radar flew between 2010 and 2015. Terrain barely moves, so the age matters less here than on most maps. It does matter for what sits on top: a district built since then reads as the ground that was there before it.

Known weaknesses

Copernicus models the land only. The sea counts as exactly zero, so the colour fades to nothing at the coastline, and land at exactly that height fades with it. Everything below it is coloured. Ocean depth needs a different source and is not on this map yet.
The detail is not the same everywhere. Where a country has published a metre-scale survey we use it, so a close-up of the Alps is sharper than a close-up of the Hindu Kush. That is a difference between survey programmes rather than between landscapes.
Radar struggles over steep ground, still water and dry sand. We have not validated any of the measurement ourselves.
Heights are above the EGM2008 geoid, which is the height an atlas quotes rather than the one a GPS receiver shows.
A small number of tiles are withheld from the free Copernicus product for certain countries.

Source and licence

Elevation from the Copernicus DEM GLO-30, delivered as terrain tiles built and served by Mapterhorn.

produced using Copernicus WorldDEM-30 © DLR e.V. 2010-2014 and © Airbus Defence and Space GmbH 2014-2018 provided under COPERNICUS by the European Union and ESA; all rights reserved. The organisations in charge of the Copernicus programme by law or by delegation do not incur any liability for any use of the Copernicus WorldDEM-30.

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