GPX files are supposed to be the universal GPS format, but in practice they come in different flavours — some missing data, some malformed, some exported incorrectly by the source app. If your GPX file isn't loading or isn't showing the data you expect, this guide covers the most common issues and how to fix them.

1. File Won't Load At All

Symptom: The tool shows an error when you drop the file, or nothing happens.

Causes and fixes:

The file is actually a FIT file renamed as GPX Some apps export FIT files but label them differently. Check the actual content: open the file in a text editor (Notepad, TextEdit, VS Code). A valid GPX file starts with <?xml or <gpx. If you see binary characters, it's not a GPX file. Use Stamptivity Convert to convert the FIT to GPX.

The file is a ZIP archive Strava exports a .zip file containing a .gpx inside. Extract the ZIP first, then use the .gpx file.

The XML is malformed Occasionally apps export broken XML — unclosed tags, invalid characters. Open the file in a browser (drag it to a browser tab) — if the browser shows an XML parse error, the file is malformed. Try exporting again from the source app.

2. No GPS Coordinates — Map Is Empty

Symptom: The file loads, but the map widget is blank, or stats show but there's no route.

This is normal for indoor activities Treadmill runs, trainer rides, and gym workouts have no GPS. The file may contain heart rate, cadence, and time, but no lat/lon coordinates. Everything except the map and route-based calculations (distance, speed from GPS) will still work.

GPS was not enabled during recording On GoPro, GPS must be switched on in settings before recording. On Garmin, GPS mode must be set (not Indoor). Check your device settings for the next recording.

The coordinates are all 0.000000, 0.000000 This means the device didn't get a GPS lock before recording started. It's most common when you started recording immediately after powering on, before the GPS antenna acquired satellites. Wait for the GPS icon to show a solid lock on your device before starting an activity.

3. Wrong Distance or Speed

Symptom: The distance or speed in Stamptivity doesn't match what your device showed.

Units mismatch Check that your preferred unit (km vs. miles) is set correctly in the tool.

GPX only stores raw coordinates — distance is recalculated Stamptivity calculates distance by summing the distances between consecutive GPS points. If your device's displayed distance used a different calculation (e.g., from a foot pod or wheel sensor), there may be a small difference.

Too few GPS points Some apps export a simplified GPX with fewer track points to reduce file size. This degrades distance accuracy because straight-line approximations are used between sparse points. Export at full resolution when the option is available.

4. Heart Rate, Cadence, or Power Not Showing

Symptom: Stats gauges appear empty or the fields show "N/A".

Using a GPX instead of FIT Standard GPX does not include power data, and heart rate and cadence support varies by exporter. If you need power, cadence, or reliable heart rate, export the original FIT file from your device instead of GPX.

Garmin Connect: gear icon → Export Original (FIT, not GPX)
Wahoo: USB from device, activities folder

The field wasn't recorded Heart rate only appears if you had an HR monitor connected during the activity. Power only appears if a power meter was paired. The data has to be recorded to be exported.

Strava strips extended data Strava's GPX export does not include power data and may not include cadence. Export from the original device for full data.

5. Wrong Timestamp / Timezone Issues

Symptom: The GPS trace looks right, but timestamps are off by hours.

GPX files store timestamps in UTC. Stamptivity displays times relative to the data in the file. If your device clock was in local time rather than UTC when it recorded, timestamps may appear shifted. This is a display issue and doesn't affect the GPS overlay alignment.

For video sync in the Overlay tool, what matters is the relative timing within the file, not the absolute timestamp. The time offset slider handles any systematic shift.

6. Route Looks Wrong — Jumps or Zigzags

Symptom: The map shows strange straight-line jumps or zigzag artifacts in the route.

GPS dropout If your device lost signal (tunnel, tree canopy, building) and then reacquired, the GPX may have a straight line between the last known position and the next lock. This is normal and not fixable without editing the file.

Poor GPS accuracy at high speed Ski runs, cycling descents, and motorsport recordings can show position drift because GPS updates at 1Hz (once per second) — at 100 km/h, that's 28 metres per update, which can produce jagged lines on tight corners.

Fix with GPX editing tools Tools like GPSBabel or online GPX editors can remove outlier points and smooth the track. This is optional — the stats calculation is usually not significantly affected by a few noisy points.

7. File Size Is Huge

Symptom: The GPX file is hundreds of MB, which is unusual.

A typical 2-hour cycling GPX at 1-second resolution is 2–5 MB. Very large files usually indicate:

Accidentally combining many activities
Recording at extremely high frequency
Embedded photo or video data (shouldn't happen in GPX, but some apps add extra metadata)

Use Stamptivity Convert to convert to a clean GPX via FIT conversion, which strips unnecessary metadata.

Quick Diagnostic Checklist

Problem	First thing to check
File won't load	Open in text editor — does it start with `<?xml`?
No map	Was the activity outdoors with GPS enabled?
Wrong distance	Units setting, and whether GPS lock was acquired
No heart rate	Do you have a FIT file instead of GPX?
No power	FIT file required; power meter must have been recording
Timestamps off	Expected — display offset, doesn't affect video sync
Route has jumps	GPS dropout, normal for tunnels and tree cover

GPX File Not Working? How to Fix Common GPX Problems