How to fix Strava activities with incorrect GPS data

I’m a fairly regular Strava user, but sometimes activities don’t track very well. It seems like phone GPS sometimes has a crazy moment where it thinks you’ve jumped around all over the place. This can often mean that your times and distances don’t make any sense. For example, Strava thinks you did a run at a pace of 5 minutes per kilometre, with one section at 2 minutes per kilometre. You might not always notice, but sometimes your best efforts can get corrupted by sections that were faster than any human could run or ride.

If the dodgy section is at the start or end of an activity, you can use Strava’s crop tool, but if it’s in the middle, Strava doesn’t let you edit it out. However, there is a way to do it manually. It’s a bit of a faff, but if you’re as anally retentive about me, you might find this useful.

Here’s how to fix Strava activities where the GPS has gone a bit haywire:

  1. From the activity page on Strava, click the Actions button (the wrench icon) and select Export GPX
  2. Click the Actions button again and delete the activity (you need to do this because you’ll be re-uploading it after editing, and Strava will think it’s a duplicate)
  3. Open the downloaded file in a basic text editor
  4. Go to https://wtracks.appspot.com and load in the downloaded file
  5. In the View menu, select "Show track markers" and wait for them to finish rendering
  6. Click on the first marker of the bad segment, and make a note of the latitude and longitude
  7. In your text editor, find the marker with that position, and add a blank line before it. If you’re not familiar with how GPX files work, there’s an example of the XML format below
  8. In wtracks, click on the last bad marker, and make a note of its latitude and longitude
  9. Back in the text editor, find that marker, and add a blank line after it
  10. Delete the blank lines and all the markers between them
  11. Save the GPX file
  12. In Strava, click the plus sign at the top right, and choose Upload Activity
  13. Select File, and upload your edited file
  14. Job done

Here’s an example waypoint marker from a GPX file:

<trkpt lat="51.4540050" lon="-0.0482360">
  <ele>50.0</ele>
  <time>2016-06-01T06:02:53Z</time>
</trkpt>
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