Under trees, in a gorge or between tall buildings a GPS sometimes drops a point kilometres away and jumps back a second later. Those spikes wreck your distance and your top speed. This throws the outliers out: anything that would need an impossible speed to reach disappears — the rest of your track stays untouched.
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.
How does it decide what an outlier is?
From the speed between consecutive points. Anything faster than the value you set can't have been travelled and is dropped. Without timestamps a distance rule applies instead (jumps over 5 km).
Which top speed should I set?
Roughly double your realistic maximum: about 60 km/h for hiking, 150 for cycling, 400 for flights. That safely catches real glitches without touching honest fast passages.
Can it delete good points?
Only if you set the value far too low. Start and finish always stay. Check the distance afterwards — it should drop by exactly the nonsense.
Which formats can I load?
GPX, FIT, TCX, KML, KMZ, GeoJSON and NMEA — download as GPX, KML, KMZ, TCX, GeoJSON or CSV.