A photograph used to be an image. Now it is an image and a small pile of facts about the moment it was made.
Inside almost every file your phone produces is a block of metadata called EXIF: the date and time to the second, the make and model of the device, the exposure, the focal length, whether the flash fired. And, if location services were on, the latitude and longitude, often to a handful of metres, sometimes with altitude and compass bearing.
Your camera roll is, among other things, a detailed map of everywhere you have been.
What that makes possible
The pleasant consequence is that photographs become browsable by place as well as by time.
This turns out to suit some collections much better than a timeline does. Travel is the obvious one: a year of trips is far easier to think about as pins on a map than as a chronological scroll. So is anything repeated in one location — a coastline photographed across seasons, a city returned to over a decade.
It also supports a kind of looking that the scroll cannot. Zoom out and you see the shape of where you actually go, which is usually smaller and more repetitive than anyone imagines. Zoom in on a place you visited once and the photographs come back attached to the street they were taken on.
For photography more broadly, geotagging is what makes it possible to explore a place through other people's images plotted where they were made, rather than through a search result ranked by popularity. You get the coastline as it was photographed along its length, not the six famous viewpoints.
What it gives away
The same precision that makes this useful is a genuine privacy problem, and it is worth being blunt about it.
A photograph taken in your kitchen carries your home address, to the metre, in a field most people have never opened. A picture of a child in a garden carries the garden. A run of images taken over a fortnight carries your routine — where you live, where you work, when you are out, the gym, the school gate.
Two things soften this in practice. Most major social platforms strip EXIF location on upload, so posting a photo publicly does not usually publish your coordinates. And iOS lets you remove location when sharing: in the share sheet, Options, then turn Location off.
Two things sharpen it. Messaging apps, email attachments and cloud links often preserve the original file intact, metadata and all. And "most platforms" is not "all", nor is it a promise about any particular one next year.
The reasonable position is not to switch geotagging off. It is genuinely useful, and photographs without dates or places become much harder to make sense of later. The reasonable position is to know it is there, strip it when you are sharing something taken at home, and be careful about which applications get wholesale access to the library.
A note on trusting the coordinates
Geotags are approximations dressed as precision.
Indoors, in cities, or in deep valleys, the phone falls back on wifi and cell positioning, which can be out by tens or hundreds of metres. Photographs taken in quick succession sometimes land in slightly different places. Screenshots, scans and images received from other people carry either nothing or somebody else's location.
So a map of your photographs is a good picture and a bad witness. Fine for browsing. Not evidence.
Where the app comes in
Photo Geographic is built around the browsing side of this: photographs from around the world plotted at the coordinates where they were taken, explored on a map and a globe rather than in a list.
It is a quiet app for looking at places. Coastlines, cities, mountains and landmarks, positioned where they belong, with no feed and no accounts.
If nothing else here is useful, this might be: open any photograph in your library, swipe up, and see what your phone recorded alongside the picture. Most people are surprised by how much is there.