Adding GPS location to hiking photos after the fact

The short answer

Yes, with one condition: a recorded track of the walk has to exist. A GPX track carries a timestamp on every point, and a photo carries its own capture time in its file metadata whether or not it has a coordinate. Line the two clocks up and you can look up which point on the track was closest in time to when the photo was taken, then use that point's coordinate as the photo's location. No location was ever inside the photo file to begin with — it gets borrowed from the track instead.

What this cannot do is invent a track that was never recorded. Matching only works because a route with timestamps already exists to match against. A photo taken on a walk that nobody tracked has nothing to be placed onto.

What you need for this to work

• The photo's own capture timestamp, which the camera writes into its metadata automatically and does not depend on Location Services at all — this is separate from the GPS coordinate field, and it is almost always present.
• A GPX track, or an equivalent recorded route, covering the time the photo was taken, with timestamps on its points.
• Both clocks reasoned about on the same footing. GPX timestamps are UTC by convention; a camera usually stamps local time. Get the offset wrong and every match lands on the wrong point.

How the matching actually happens

A geotagging tool

This is a well-worn category of tool, built specifically to read a photo's capture time, find the nearest timestamp in a GPX track, and write that coordinate back into the photo's own metadata. ExifTool, a long-standing free command-line tool, has a geotagging mode built for exactly this. Some photo management software includes the same idea under a name like "track sync" or "geotag from GPS log." The mechanics are always the same: two timestamps, one lookup, one coordinate written back.

By hand, for one or two photos

For a small number of photos this does not need a tool at all. Open the GPX file in a text editor or a map viewer that shows raw points, find the timestamp closest to the photo's own capture time, and read off the latitude and longitude sitting next to it. It is tedious past a handful of photos, but it is exact, and it needs nothing more than the file itself.

Where it goes wrong

• Timezone mismatch: comparing a UTC track timestamp directly against a local-time photo timestamp lands every match hours away from where it should be. Convert one to match the other before comparing anything.
• Clock drift: a camera's clock and a GPS device are two separate clocks. A few minutes of drift between them, built up over weeks without being reset, quietly shifts every match along the route.
• Gaps in the track: a stretch where recording was paused, or where the fix was lost, has no points to match against. A photo taken inside that gap cannot be placed with any confidence — the nearest surviving point is only a guess at how far away the real position was.

What this does not fix

A voice note matched this way still has no location field of its own — Voice Memos and similar recorders do not carry one, so even a successful match only tells you where the recording sat on the route; it does not change the file itself the way writing a coordinate into a photo does. You would need to keep the pairing as a separate note.

And matching after the fact only recovers where something happened, not the fuller context that comes from being pinned to the route while it was still recording — how far into the walk it was, or what the climb looked like right around it. That context comes from the original recording, not from a coordinate reconstructed afterwards.

What TrailCam does

TrailCam avoids needing any of this by pinning a photo, a video clip of up to two minutes, or a spoken voice note to the route at the moment it is captured, from inside the recording screen. There is no metadata to reconstruct afterward and no clock to line up, because the location was never missing in the first place. It is free to download.