How track-based geotagging works
Every photo stores the exact time it was taken in its EXIF metadata. Every point in a GPX track stores a time and a set of coordinates. Geotagging means finding, for each photo, the track point closest in time and writing those coordinates into the image file.
Nothing else is needed: no connection, no manufacturer app, no landscape recognition. Just the track and the photos.
The critical step: your camera's clock
This is where 90 % of attempts go wrong. If your camera's clock is off, every photo will land at the wrong point on the route, systematically shifted. The two usual culprits:
- Time zone: GPX stores times in UTC, while your camera records local time. In mainland Spain that is one or two hours of difference depending on the season.
- Clock drift: a camera that has not been set for months can be several minutes fast or slow.
There is a classic and very effective trick: at the start of the walk, photograph your phone's screen showing the time. Compare that photo against its own EXIF timestamp and you know exactly what offset to correct.
Load your track and your photos, and let GEPYX place them along the route.
Open the GEPYX editorDoing it in GEPYX, step by step
- Open the editor and load the route's GPX.
- Add the photos you want to geotag.
- GEPYX reads each image's EXIF timestamp and places it along the track. If they all appear shifted, adjust the time offset and they reposition.
- Check on the map that the photos land where you expect: the summit shot, on the summit.
- Download the images with the coordinates already written into their EXIF.
All of it happens inside your browser. The photos are never uploaded to a server, which is not a minor detail when you are dealing with personal images carrying location data.
What it is good for afterwards
- Map search: Lightroom, Apple Photos and Google Photos automatically place geotagged images on their map view.
- Route write-ups: you can illustrate a track knowing exactly which kilometre each photo was taken at.
- Long-term memory: in ten years you will not remember which pass that was. The EXIF will.
A privacy warning
Geotagging is genuinely useful, but remember that the information travels inside the file. If you publish the photos, you are publishing exact coordinates. Be especially careful with images taken at home or where you parked, and with sensitive places such as shelters or nesting areas. Many social networks strip EXIF on upload, but not all of them, and a file sent by email or messaging usually keeps it intact.