What happens to a GPS track if your phone dies mid-hike

The short answer

The track stops at the last point recorded before the battery ran out. Everything up to that instant — distance, time, elevation, any photos or notes captured along the way — is already written to the phone's storage and is not affected by the power loss. Nothing after that point exists, because it was never captured in the first place; there is no missing chunk to recover, only a walk that stopped being recorded a bit earlier than the walk itself actually ended.

Why the file does not just disappear

A recording app that is any good does not hold an entire hike in memory and write it all out at the end. It writes points to disk continuously, as they come in, precisely so that a crash, a force-quit or a dead battery only costs the most recent moment rather than the whole session. By the time the phone actually powers off, almost everything you walked is already sitting in permanent storage, independent of whatever state the app or the OS was in at the instant power was lost.

This is also why a dead battery and a full, tidy save are not opposites — they are the same mechanism, just stopped at different points. A hike that ends normally is not "saved" by some special final step that a dead battery skips; it has been saving the whole time, and ending normally just means the last of those routine writes happened to be the actual end of the walk.

What comes back when the phone turns back on

Once the phone is charged and powered on again, the recorded portion of the hike is exactly where it was — same distance, same elapsed and moving time, same elevation profile, up to the last point saved. Distance and time are not extrapolated forward to guess at the missing stretch; a hike that dies at the halfway point reports roughly half the real distance, not the full distance you actually covered, because the app has no way to know what happened after it stopped recording.

A GPX or CSV export made from that hike afterwards reflects the same thing: a complete, valid track file for the part that was recorded, ending abruptly rather than at the trailhead you actually finished at.

The same thing happens for reasons other than a dead battery

• Force-quitting the app mid-recording — the track is cut off at whatever was last written to disk, the same as a dead battery.
• An iPhone restarting on its own, or being restarted manually, partway through a walk.
• The app crashing outright — a rare event, but one that behaves identically from the track's point of view: everything already saved survives, nothing after that moment does.
• Airplane mode, Low Power Mode and losing cell signal are different from all of these — none of them stop a GPS recording or affect what gets saved, so they are not a cause of a cut-off track.

Cutting the risk down, not eliminating it

There is no way to record a track after the phone has no power to record it with, so the only real lever is not running out of battery in the first place. A small power bank in a pack covers most of what a long day actually needs. Turning down screen brightness, closing apps you are not using, and understanding what actually drains a phone's battery on a hike — GPS itself is a modest part of it, screen time and cellular search in poor coverage areas usually cost more — does more for battery life over a full day than anything you can do after the fact.

Where TrailCam fits in

TrailCam saves a route as it records rather than only at the end, and if the app is ever interrupted mid-walk, it offers the unfinished route back to you the next time you open it — so a dead battery costs you the rest of that specific walk, not the record of it. The app is free to download.