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Comment by sklivvz1971 | Hacker News Reader

sklivvz1971

3. Why is my iPhone logging my location?

The iPhone is not logging your location. Rather, it’s maintaining a database of Wi-Fi hotspots and cell towers around your current location, some of which may be located more than one hundred miles away from your iPhone, to help your iPhone rapidly and accurately calculate its location when requested

This actually makes sense - looking at the logs on my iPhone and iPad, the locations where pretty far away from the places where I usually roam, and actually there was a very great deal of places where I've never been, not even close.

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>and actually there was a very great deal of places where I've never been, not even close.

How does that make sense? It should only cache the locations of cell phone towers it was in the range of. Are you seeing data that was more than 100 miles away from the places you were at?

> Are you seeing data that was more than 100 miles away from the places you were at?

Yes, actually. I used the app that was posted and, even after I modified the code to stop fuzzy-ing the data, I was thinking to myself "well, I've never been anywhere close to there".

I live in the south of England and some places were in the north. Yes, I would say some of the locations are 100 miles away from me at all times.

Nope. It's a local (geographically speaking) slice of a huge database of hotspots. There is a concentration of points downtown, a few points at the local airport, others at touristic destinations nearby. Most are places I've never been at.

It is nothing but a very neat cache. The nerd in me is sad to see it go.

Is it possible the cell tower you're locally connected to is aware of its adjacent towers and communicates this information back to the iPhone? If you're traveling at highway speeds, or perhaps on rail, a 100 mile radius won't cover a huge area. Looking at my own data it seemed to be closer to 200-300 miles in some cases. (in rural areas where presumably towers are spaced out further apart)

Ever go up in a tall building? Your phone sees more towers. But actually, we don't know that "towers my phone sees" is the actual mechanism here.

Apple hasn't explained the algorithm they use to determine what location data to send to the phone. Perhaps they're saying "100 miles" because that's what they do -- send tower data for up to 100 miles around the current tower, depending on tower density for that location.

So - while your current location isn't logged, enough data is logged to derive your current location?

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