Why does a GPX file get bigger the longer you record?

The short answer

A GPX track is a sequence of points, and each point is logged at roughly the same rate the whole way through a hike. Walk for twice as long and, all else equal, you end up with roughly twice as many points, each one adding its own small, fairly constant number of bytes to the file. File size scales with how long you recorded, not with how far you walked or how interesting the route was.

What one point actually costs

GPX is plain-text XML, not a compact binary format, so every point is written out as readable tags and numbers rather than packed bits. A single track point typically carries a latitude, a longitude, an elevation and a timestamp, each wrapped in its own tag with a bit of surrounding structure. That is maybe a hundred bytes of text per point once you add it all up — not much on its own, but it repeats for every single point in the track.

A short walk with a few hundred points might produce a file measured in tens of kilobytes. A long day out with several thousand points scales that up proportionally. Neither number is large by the standards of a modern phone, which is part of why GPX file size rarely matters in practice, but the relationship between duration and size is real and easy to see once you know what is being counted.

Why duration matters more than distance

It is tempting to assume a longer route causes a bigger file, but the more direct driver is time, not ground covered. A recording app logs points against a roughly steady rate as the clock runs, whether you are covering ground quickly on a downhill stretch or moving slowly on a steep climb. Two hikes of the same duration end up with a similar number of points and a similarly sized file even if one covered twice the distance, because what was being counted the whole time was time passing, not metres travelled.

This is also why a hike with a long lunch stop can produce a smaller file than a shorter hike with none, if the app pauses recording during the stop. A pause means no new points are being logged for that stretch, the same way it means nothing is added to elevation gain or moving time — the file only grows while the track is actively recording, not while the clock on the wall is running.

What does not make much difference

• How steep the terrain was — elevation is one more number on an already-present point, not an extra point.
• How many turns the route had — a GPX track does not treat a straight stretch and a winding one any differently; it just keeps logging points at the same rate either way.
• The activity type chosen — that is a label attached to the recording, not a change to how often points are logged.
• Whether the route was a loop or an out-and-back — file size follows time spent recording, not the shape traced on the map.

Where the real size actually comes from on a modern hike

On its own, the track — the list of coordinates — stays a modest, text-based file even for a very long hike, because plain numbers and tags compress down to very little in absolute terms. The photos, video clips and voice notes pinned along a route are a completely separate matter and are, byte for byte, vastly larger than anything in the track itself; a single video clip alone typically outweighs an entire day's worth of GPS points. If a hike's saved data feels heavy, the track is almost never why — the media pinned to it is.

Things that trip people up

• Assuming a bigger file means a more accurate or more detailed track — it usually just means a longer recording, not a better one.
• Expecting distance to predict file size — duration is the closer match, since points are logged against time rather than metres covered.
• Blaming file size on hilly terrain or a winding route — neither adds points on its own; only time spent actively recording does.
• Worrying that a large GPX file will be hard to open or upload — even a long day's track is plain text and small by modern standards; it is attached photos and video that actually add weight to a saved hike.

Where TrailCam fits in

TrailCam records your route as a track for the whole time you are moving, pauses it when you pause, and exports the result as a standard GPX 1.1 file whenever you ask for it. The track itself stays a modest export regardless of how long the hike ran; it is the video clips, photos and voice notes pinned along the way that make up the bulk of what a long hike actually stores. TrailCam is free to download.