Does a GPX file record your speed?
No, not as a field of its own. A GPX track point is built from position, usually an elevation, and usually a timestamp â that is the closed list the schema gives it, and speed is not on it. That does not mean speed is unknowable from a GPX file, though: unlike something a GPX file genuinely has no way to capture, speed can always be worked back out afterward, because the two things it is made from â distance between points and the time between their timestamps â are already sitting right there in the file.
The short answer
GPX 1.1 defines a fixed set of fields for a track point, and speed is not one of them. A point carries latitude and longitude, usually an elevation, and usually a timestamp â the same short list that shows up whether the file came from a phone, a dedicated GPS unit, or GIS software. If a speed figure shows up on a map or a chart after a GPX file is opened somewhere, that number was calculated by whatever app opened it, not read directly out of the file.
What a track point actually carries
Position, elevation and time cover the three things almost every reader of a GPX file needs, and they are the three fields the format has carried since it was first published. That short, closed list is exactly what keeps GPX portable between very different pieces of software â Strava, Garmin Connect, Komoot and a GIS package can all open the same file and agree on what every field means, because the list of fields they need to agree on was kept small on purpose.
Why speed didn't need a field of its own
Some things a GPX file simply has no way to remember â the weather during a hike, say, which has no relationship to position or time that a later reader could reconstruct. Speed is a different case. Distance between two consecutive points and the time gap between their timestamps are both already in the file, and speed is nothing more than one divided by the other. Giving speed its own field would have meant storing a number that can always be rebuilt from data the file was going to carry anyway, so the schema simply left it as something to work out afterward rather than something to log at the time.
Why the same file can show two different speeds
Because speed is never stored, it is never just read back either â every app that shows it is running its own calculation over the same raw points, and small differences in how that calculation is done show up as a different number even though the underlying file never changed. One app might work speed out point-to-point, between two consecutive positions a second or two apart. Another might smooth several points together first, to soften the jitter that ordinary GPS noise puts into any short gap between two closely spaced points. Neither is reading a stored figure off the file; both are doing arithmetic on the same position-and-time data and getting a slightly different answer, which is a large part of why the same GPX file can end up with a different speed, or a different pace, in two different apps.
The one place a stored speed could hide
GPX does allow an optional extensions block on a point, meant for exactly the kind of data the core schema never defined a field for, and some devices do write a speed reading into one. Even then, an extensions block is only readable by software that recognises the specific namespace it was written under â a different app opening the same file is free to skip straight past it. A speed value tucked into extensions is not something you can count on surviving a move from the app or device that wrote it to anything else that opens the file afterward.
Where TrailCam fits in
A route exported from TrailCam is a plain GPX 1.1 file â position, elevation and time on every point, the fields every reader already knows how to open, without a speed value bolted on through an extensions block that only round-trips correctly through TrailCam itself. Pace and distance are worked out and shown inside TrailCam from its own recorded points, the same way any app calculates them; the exported file just carries the raw track underneath. GPX and CSV export are part of the optional TrailCam Pro upgrade; the app itself is free to download.
Questions
- Does a GPX file store pace instead of speed?
- No, for the same reason â pace is also arithmetic done afterward, in this case distance over moving time, rather than a value any version of the GPX schema has a field for. Nothing about pace changes that; it is calculated by whatever app or spreadsheet is looking at the file, not stored inside it.
- If speed is not in a GPX file, how does an app show a speed graph after importing one?
- It calculates one. The app steps through the track points in order, works out the distance and time gap between each pair, divides one by the other, and draws the result as a graph. That calculation happens the same way every time a GPX file without a speed extension is opened â the graph is built fresh from position and time, not pulled from a stored number.
- Can I add a speed value to a GPX file myself?
- Only informally, inside an extensions block, and there is no guarantee anything other than the software that wrote it will read that value back correctly. For a number you want to survive a move between tools, it is more reliable to let whichever app opens the file calculate speed from position and time itself, since that calculation works the same way in any GPX reader.
Recording your own routes
TrailCam is an iPhone app that records your route with GPS, keeps video clips, photos and voice notes pinned to the spot where you took them, and exports the result as GPX 1.1 or CSV. It is free to download.