About Terrainly

Terrainly is a small independent project with one goal: make it effortless to look at elevation data, without installing GIS software, creating an account, or uploading anything.

Why it exists

Elevation files are everywhere (drone surveys, lidar downloads, government datasets) but just checking one usually means launching heavyweight desktop software. A lot of the time you only want to know: is this the right file, and does it look right? This viewer answers that in seconds.

Principles

• Private. Files are processed in your browser and never uploaded. See the privacy page.
• Honest. It is a visualization tool. It does not claim survey-grade accuracy, and it tells you when it can’t read a file instead of failing silently.
• Tested on real data. Not only tidy sample files: lidar tiles, files in unusual projections, feet instead of metres, NoData holes and rasters with over a hundred million cells.
• Simple. No sign-up, no clutter, and one clear job.

What’s next

Planned additions include an aspect map, elevation profiles, measuring tools and cut and fill volumes. The list is on the home page.

Credits and open-source software

This site stands on the shoulders of excellent free software and open data:

• geotiff.js (MIT) reads GeoTIFF files in the browser, and fzstd (MIT) decodes ZSTD-compressed ones.
• proj4js (MIT) converts between coordinate systems, using definitions from the EPSG registry via epsg-index (ISC).
• Leaflet (BSD-2-Clause) draws the map.
• Base map © OpenStreetMap contributors, © CARTO.
• Sample terrain: High Resolution Digital Elevation Model (HRDEM), Natural Resources Canada. Contains information licensed under the Open Government Licence – Canada.

Contact

Questions, bug reports (especially a file that won’t open) and ideas are welcome: [email protected]. Please don’t attach confidential files.