# Unrealistic elevation gain after FIT import due to initial altitude spikes

**URL:** <https://forum.intervals.icu/t/unrealistic-elevation-gain-after-fit-import-due-to-initial-altitude-spikes/133510>\
**Category:** Bug Reports\
**Created:** [7 November 2026 16:06 UTC](https://forum.intervals.icu/t/unrealistic-elevation-gain-after-fit-import-due-to-initial-altitude-spikes/133510 "2026-11-07T16:06:32Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Frasodel](https://forum.intervals.icu/user_avatar/forum.intervals.icu/frasodel/32/46768_2.png) [@Frasodel](https://forum.intervals.icu/u/Frasodel)\
**Post date:** [7 November 2026 16:06 UTC](https://forum.intervals.icu/t/unrealistic-elevation-gain-after-fit-import-due-to-initial-altitude-spikes/133510/1 "2026-11-07T16:06:32Z")

</div>

Hi,

When I upload `1794041449-GIR.fit` to Intervals.icu, it shows approximately 500 m of elevation gain for a run of just 1.23 km lasting 7 minutes 13 seconds.

An analysis of the FIT file identified abnormal altitude readings during the first 10 seconds:

| Time from start | Recorded altitude |
| --- | --- |
| 0–1 s | 590.8 m |
| 2–3 s | 0 m |
| 4 s | 539.8 m |
| 6 s | 532.4 m |
| 7 s | 518.0 m |
| 9 s | 496.6 m |
| 10 s | 489.4 m |

After that, the altitude readings become consistent, with small, gradual changes. Summing the altitude changes from the 10-second mark onwards gives approximately **10.2 m of ascent and 15.2 m of descent**. These are estimates for the remaining activity, rather than verified totals for the entire run.

The source file clearly contains faulty initial readings, but Intervals.icu appears to include the resulting spike in its elevation gain calculation.

Could you investigate whether these implausible altitude jumps can be detected and excluded during import, or suggest an existing way to correct the elevation data?

The issue can be reproduced by importing the original FIT file, which I can provide for troubleshooting.

Thanks!

---

<div class="post-metadata">

**Author:** ![MedTechCD](https://forum.intervals.icu/user_avatar/forum.intervals.icu/medtechcd/32/40383_2.png) [@MedTechCD](https://forum.intervals.icu/u/MedTechCD)\
**Post date:** [7 November 2026 16:35 UTC](https://forum.intervals.icu/t/unrealistic-elevation-gain-after-fit-import-due-to-initial-altitude-spikes/133510/2 "2026-11-07T16:35:55Z")

</div>

Zoom to time range that needs correction - Actions - Fix Data

> [@Climbing calculation error](https://forum.intervals.icu/t/climbing-calculation-error/114909/3):
>
> Zoom to the first couple of seconds, then use Actions - Fix data, and apply a function for Elevation where you set the visible part to a fixed altitude. I used 100 in this example This will correct the first second(s) of incomplete data from your device. My Coros watch has this same behaviour and logs 0 elevation until the GPS signal is locked and I’m moving. Another option is to crop the activity so that the first second(s) are no longer part of it. Zoom to what you want to keep and…

Set first ten seconds to 490m for example in your case.