Does GPS accuracy depend on what country you're in?

The short answer

No. What determines how clean a GPS track looks is the geometry of the satellites overhead and whatever is physically standing between the receiver and the open sky at that moment — tree cover, a tall building, a narrow valley, bad weather. None of that is assigned by country. A walk through dense forest produces the same kind of rough track whether the forest is in one country or another, for the same reason both times: the receiver is reacting to what is over its head, not to which country issued the passport of whoever is carrying it.

Why the satellites themselves don't recognise a border

The GPS constellation is a set of satellites in orbit roughly 20,000 kilometres up, arranged so that enough of them are visible from anywhere on the ground at any time. A receiver's job is to pick out whichever of those satellites happen to be above the local horizon at that exact moment and location, then work out a position from the tiny differences in when each one's signal arrives. Nothing in that process reads a map or checks which country the receiver is currently standing in — a border is a line drawn for people, and it means nothing to a signal travelling down from orbit or to the chip listening for it.

What actually changes a track from one hike to the next

The things that really do move a track's accuracy up or down are all local and physical, and every one of them can show up in any country:

• Dense tree cover, which blocks part of the sky regardless of which side of a border it's growing on.
• Tall buildings or a narrow canyon, which block some satellites and bounce the rest off hard surfaces before they arrive.
• Mountainous terrain, which can hide a chunk of the sky behind a ridge in one direction.
• Bad weather, which affects reception a little on any hike, anywhere.
• Where the phone is carried, since a body or a bag blocking the antenna works the same way on every continent.

Two walks on two different days in the same city can end up further apart in accuracy than one walk in each of two different countries, because the list above is decided by that day's terrain and weather, not by a national border.

The one place a country really does show up — the map, not the GPS fix

There is exactly one country-shaped exception, and it sits downstream of the GPS fix rather than inside it. Mapping regulations in mainland China require publicly available maps to plot positions on a deliberately shifted grid rather than the raw coordinate a GPS receiver produces, for reasons that have nothing to do with measurement accuracy. A route recorded there can look visibly shifted — sometimes by a distance large enough to notice on the map — once it is drawn on a map service built to that local requirement, even though the underlying position was measured just as accurately as it would be anywhere else.

The coordinate itself never moved. What changed is only where one particular kind of map chooses to draw it. A GPX file's coordinates are written in the same global reference system GPS itself uses — WGS-84 — no matter which country a hike happened in, so a file exported from a walk anywhere in the world opens in the right place in any standard GPX reader elsewhere. The mismatch only ever shows up on the small number of maps deliberately built to a shifted local grid, never in the recorded file.

Where TrailCam fits in

TrailCam records a route with GPS the same way wherever a phone happens to be, because the receiver is listening to whichever satellites are overhead at that moment, not checking which country's network the phone is registered on. A hike recorded anywhere exports as a standard GPX 1.1 file using the same global coordinates a hike recorded anywhere else would use. Export is part of the optional TrailCam Pro upgrade; the app itself is free to download.