Google Photos uses ML to tag photos and this feature released amidst much fanfare at Google I/O a couple of years ago. They don't need location data to geotag photos anymore.
They took 126 million geotagged images from the web, bined them into 26,000 squares, and trained a neural net to predict which square on the earth an image was taken in. That's very poor resolution, but if you see that 20 images taken around the same time are tagged as the square that contains San Francisco, you can be pretty sure they all happened during a trip to San Francisco.
Thanks for explaining one possible method. It could still mean Google is tracking location "without consent". I suppose it depends on whether they use that location data for anything other than Google Photos.
They took 126 million geotagged images from the web, bined them into 26,000 squares, and trained a neural net to predict which square on the earth an image was taken in. That's very poor resolution, but if you see that 20 images taken around the same time are tagged as the square that contains San Francisco, you can be pretty sure they all happened during a trip to San Francisco.
Reminds me of https://geoguessr.com