Many phones record tracks without any elevation, and GPS altitude is notoriously noisy — a flat ride suddenly claims 800 m of climbing. This tool looks the altitude up in a terrain model instead: Europe at 25 m resolution, worldwide at 90 m. It can fill only the gaps or replace everything to de-noise the profile. One heads-up: this is the only tool here that queries an outside service (opentopodata.org) — about one sample every 90 metres is sent, never your whole track.
FAQ
What happens to my file?
Your file is sent to the Reisezoom server for processing, handled there and deleted immediately — nothing is stored. So that the web tool and the desktop app arrive at the same number, both use the same component — and that one runs on the server.
Where does the elevation come from?
From open terrain models: EU-DEM (Europe, 25 m grid) or SRTM (worldwide, 90 m grid) via opentopodata.org. The tool samples anchor points every ~90 m along your track and interpolates between them.
Fill gaps or replace everything?
“Only fill gaps” keeps your barometer readings and completes the rest. “Replace all” swaps every value for terrain data — the right choice when your ascent numbers are obviously inflated.
Why does the ascent drop after replacing?
Because GPS noise is gone. A drop from, say, 277 m to 232 m on the same tour means the difference was measurement jitter, not real climbing.
What about bridges and tunnels?
A terrain model only knows the ground. On a bridge you get the valley floor, in a tunnel the mountain above you. For those passages, recorded barometer data is better — use “only fill gaps”.