Instrument 02
GPX File Audit: Check Elevation, GPS Errors and Bad Ride Data
Every recorded point walked in order, and every fault the recording left behind reported in place.
A GPX file audit reads an activity the way the device wrote it, point by point, and checks whether the sequence describes something physically possible. Position jumps, elevation spikes and recording gaps each leave a distinct signature in the file, and each one is unmistakable once something has actually counted them.
Open a file for the GPX file audit
or drag one onto this panel
Audit result
| Quantity | Value |
|---|---|
| Recorded points | 0 |
| Distance | 0 km |
| Elapsed | 0 |
| Moving | 0 |
| Climbing, raw sum | 0 m |
| Climbing, smoothed | 0 m |
| Fastest point-to-point | 0 km/h |
| Check | Result | Status | Note |
|---|
What the GPX file audit checks, and why each one matters
Eight checks run over the track. Three concern position and speed, three concern time, and two concern the completeness of the GPX record itself. None needs to know anything about you or the route, which is why a GPX file audit works on any activity from any device, whatever produced it.
Elevation spikes and inflated climbing totals
A barometric altimeter responds to pressure, and pressure responds to weather, tunnels, doorways and a gust hitting the sensor. When altitude moves twelve metres while the bike moves under forty, something other than a hill caused it. Enough of those and a flat ride reports several hundred metres of climbing.
The audit reports raw and smoothed totals side by side for this reason. On a clean file the two agree within a few percent. A wide gap is the clearest available evidence that the altitude channel misbehaved, and it explains most arguments about why one rider's GPS errors produced a different total.
GPS errors: position jumps and impossible accelerations
Satellite signals bounce. A receiver in a city centre or under dense woodland can resolve a position that is confidently wrong by a hundred metres, then correct itself a second later. Both corrections appear in the file as motion, and the arithmetic reads them as a sprint no rider could ever have produced.
Accelerations are checked separately because they catch a different fault. Going from walking pace to racing speed inside two seconds is not a signal error but a splice, a paused recording resumed elsewhere, or a device that lost and regained lock. The distinction matters when a segment result is disputed.
Recording gaps, reversals and missing channels
Time is supposed to increase. When it does not, the file has been edited, merged or written by a device with a confused clock. Recording gaps longer than a minute usually mean auto-pause or a flat battery, and any average computed across one silently blends two separate pieces of riding into a single figure.
The GPX file audit reports position jumps and recording gaps separately for that reason. They look similar in a summary and mean different things: one is a receiver briefly deceived, the other a stretch of riding the device never saw at all, and only the second leaves a hole in the elapsed time.
GPX file audit questions
Is my activity file uploaded anywhere when I run the GPX file audit?
No. The file is read by the browser on your own machine and parsed there. No copy is transmitted, stored or logged anywhere, and closing the tab discards it completely. That follows from how the page is built. It is not a promise about a server, because no server is involved.
Which formats does the audit accept?
GPX and TCX, which are both XML and both exportable from every major tracking platform and head unit. The binary FIT format is deliberately not supported: decoding it correctly in a browser is a large job, and a converter that only half works would quietly produce misleading results, not obviously failing.
Why does the audit report two different climbing totals?
The raw figure sums every upward step between consecutive points. The smoothed figure runs a short rolling average first. Barometric noise inflates the raw number, sometimes by a third on a long ride, so the gap between the two is a direct measure of how noisy the altitude channel was.
What counts as a position jump?
Any pair of consecutive points implying more than 108 kilometres per hour. Under tree cover or between tall buildings a receiver can place you a hundred metres sideways for a second, which reads as a brief impossible sprint. Several such jumps in one ride usually mean poor reception, not anything else at all.
The audit flagged my ride. Does that invalidate it?
It does not. A flag says that figures derived from the affected points cannot be trusted, not that the ride never happened. A file with twenty elevation spikes still records a real outing; its climbing total is simply wrong, and any segment crossing those affected points inherits exactly the same error without showing it.
If the climbing total is what brought you here, why elevation comes out wrong covers the mechanism in full. For reception problems see GPS accuracy, and to judge a result instead of a file use the plausibility check.