Atlas
Where to find elevation data for a place, how to turn it into contours that read well, and what the result is good for. Written for GIS people, designers, 3D artists, architects and hikers alike, with the open-source route alongside ours.
Elevation data sources
Every open terrain model for a country or for the whole planet: who publishes it, how fine it is, which datum its heights refer to, what the licence allows and where to download it yourself.
- Global elevation models compared GEDTM30, Copernicus GLO-30, FABDEM and FathomDEM, SRTM and NASADEM, ALOS AW3D30, ArcticDEM, REMA and ETOPO 2022: surface or bare earth, epoch, height datum, licence, what independent studies found, and when to use which. Read →
- Elevation data for France RGE ALTI, LiDAR HD, BD ALTI and the European and global fallbacks: resolution, height datum, projection, licence and where to download each, plus the traps specific to French data. Read →
- Elevation data for the United States USGS 3DEP explained product by product: 1 m lidar DEMs, the new seamless 1 m, the 1/3 and 1 arc-second models, Alaska IfSAR, quality levels, datums, coverage gaps and the fastest ways to download. Read →
Guides
How to choose a contour interval and avoid the classic mistakes with elevation data, grounded in mapping standards and published research. With the QGIS or GDAL route every time, not only ours.
- How to choose a contour interval Three checks that settle the interval for any map: what your elevation data can support (the National Map Accuracy Standards rule), how close the lines get on your steepest slope at print scale, and how many lines the relief needs. With a spacing table, index contour rules and the sources behind each number. Read →
- 10 classic mistakes with elevation data Surface instead of terrain, feet read as metres, geoid vs ellipsoid, contours in degrees, hidden vertical exaggeration and five more: how each one shows up in your map, and how to catch it before it ships. Read →
Accuracy & transparency
What our contours can and cannot be used for, and how they are made.
The datasets TopoLines itself traces from are listed in the docs. Corrections and requests for a country: GitHub issues.