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GPX Fixer

GPS units lie. Cities reflect signal off buildings, mountains shadow the satellites, tunnels eat the signal entirely. The result is a recording with teleports — straight 500-meter lines through a forest — and elevation spikes that say you climbed 50 meters in two seconds.

The PeakLine GPX Fixer cleans those up automatically. Drop in a broken GPX, get back a sane one.

What it fixes

Teleport removal

The classic GPS failure: two consecutive points that imply you traveled at 200 km/h on a bicycle. The fixer applies a per-sport speed ceiling:

Activity Speed ceiling
Ride / GravelRide / MountainBikeRide 35 m/s (≈ 126 km/h)
Run / TrailRun 7 m/s (≈ 25 km/h)
Hike / Walk 4 m/s
Swim 4 m/s

Anything above is treated as a glitch and dropped. The fixer runs up to five passes, because removing one bad point sometimes exposes a second bad point next to it that was hiding behind the first.

Anchor outlier

A specific bug: your device captures the first point from inside your house (where it locked onto a weak satellite reading 500 m away), then starts recording properly once you're outside. That leaves a single bizarre first point with a giant jump to the second point. The fixer drops the first point if it's more than 500 m and more than 20× the median inter-point distance from the rest of the cluster.

Time anomalies

Some buggy devices write duplicate timestamps or backwards timestamps into the GPX. Both confuse every downstream analysis tool. The fixer drops them.

Elevation smoothing

GPS altitude has barometric drift and per-point noise of ±2–3 m even on a good unit. A MAD (Median Absolute Deviation) filter identifies single-point altitude spikes and replaces them with the rolling-window median. A 50-meter "spike" in 5 seconds gets flattened; a real climb stays untouched.

Activity classification

If the original GPX doesn't tag an activity type (or tags it wrongly), the fixer infers from the median speed and the elevation profile.

How to use it

  1. Open the GPX Fixer page.
  2. Drag and drop your .gpx file (or click to browse). Max 50 MB; multi-day adventures fit fine.
  3. Wait 2–10 seconds depending on point count.
  4. The result page shows:
    • A map with the original track in red and the fixed track in green. Removed points are highlighted with little × markers.
    • Statistics — distance before vs. after, longest removed jump, total points removed, elevation smoothing count.
  5. Click Download fixed GPX.

Use cases

  • A ride didn't sync and you have only the FIT / GPX from your device. Fix it, upload to Strava manually.
  • Strava rejected the GPX because of a timestamp gap. Run it through the fixer and it'll go in clean.
  • Your distance and elevation feel obviously wrong ("I got dropped on every climb but Strava says my power was 320 W average — that's a glitch"). The fixer often catches it.
  • Old GoPro / Garmin / Sigma files from devices that didn't sanitize their output.

Daily limits

  • Guest users: 1 fix per calendar day (UTC). Enough for occasional emergencies.
  • Email and Strava users: unlimited.

If you hit the guest limit and need more, register with email — it takes ten seconds and unlocks unlimited fixes plus saved settings.

Tips and caveats

  • Always keep your original file. The fixer is good but not infallible; an original copy lets you re-run with different settings later.
  • The fixer doesn't add data. If your device dropped the signal for 30 seconds in a tunnel, the fix interpolates a straight line through the gap. It can't conjure the real route. That said, the straight line is honest — it doesn't fake distance.
  • Heart rate and power streams pass through untouched. Only position and time are corrected.
  • Strava re-uploads keep the original timestamp. Your achievements won't shift dates.

See also