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The way it works is by triangulation. If by some reason, sometimes, you are outside the range of 3 cell towers (for triangulation), depending on what antennae they use, all they might be able to guess is a general 60/120 degree direction and a distance that has to account for attenuation, depending on what kind of ground you're in, and reflections / refractions and whatnot (specially bad in mountains / big citties / etc).. That's what produces those artifacts.

On the other hand, on most European cities you rarely find yourself outside the range of 2 or 3 cell towers (no idea on how good the coverage gets in the US).

And just because some points aren't exactly where they should be and there is one trip you say you can't account for, that might be due to a lot of factors, as in:

Bad cell tower configuration; Lousy user memory; More than one person sharing the same phone; (etc).

Any of those can't be an excuse for the lousy security of the whole procedure why generally accurate tracking of the user.

Paranoiac. http://news.ycombinator.com/item?id=2467895

Even better: http://www.willclarke.net/?p=278

there is still a large security concern for people that live in cities. Since the urban density of “cell phone towers” (or more realistically, wireless network nodes) is much greater, couldn’t someone who stole your iPhone find you in a city much more easily?

From the data I’m seeing, no. I have been looking through the table of my data more thoroughly and what I’ve found is interesting. It doesn’t log one data point at a time - it will log a couple dozen data points all at once. For example, here is my data visualized on a graph, for the timestamp of April 3rd at 5:15:25.865 PM:

Note the Horizontal Accuracy of the two points. This is a measure, in meters, of the confidence in that location - like when you load up maps and it shows a blue “halo” around your location indicating the area you may be in. The first point has an accuracy of 549 meters, the second 500 meters - and they are over 2000 meters from each other. Now, if these data points are supposed to be where you are, then their horizontal accuracies should all overlap on some point that reveals your actual location. But they don’t - which is why I believe they are locations of nearby cell sites, and the horizontal accuracy is a measure of how confident it is that the cell is there.

“But it’s still very revealing!” you must be thinking. After all, if it’s cell sites around you, you must be right in the middle of that circle. Fortunately for my privacy, no. At 5:15 PM on April 3rd I was in the bottom left of that circle, over a block away from the nearest dot on the map. I had just finished a 155 mile bike trip and was pretty happy to be sitting there, not moving.

there is still a large security concern for people that live in cities. Since the urban density of “cell phone towers” (or more realistically, wireless network nodes) is much greater, couldn’t someone who stole your iPhone find you in a city much more easily?

From the data I’m seeing, no. I have been looking through the table of my data more thoroughly and what I’ve found is interesting. It doesn’t log one data point at a time - it will log a couple dozen data points all at once. For example, here is my data visualized on a graph, for the timestamp of April 3rd at 5:15:25.865 PM:

Note the Horizontal Accuracy of the two points. This is a measure, in meters, of the confidence in that location - like when you load up maps and it shows a blue “halo” around your location indicating the area you may be in. The first point has an accuracy of 549 meters, the second 500 meters - and they are over 2000 meters from each other. Now, if these data points are supposed to be where you are, then their horizontal accuracies should all overlap on some point that reveals your actual location. But they don’t - which is why I believe they are locations of nearby cell sites, and the horizontal accuracy is a measure of how confident it is that the cell is there.

“But it’s still very revealing!” you must be thinking. After all, if it’s cell sites around you, you must be right in the middle of that circle. Fortunately for my privacy, no. At 5:15 PM on April 3rd I was in the bottom left of that circle, over a block away from the nearest dot on the map. I had just finished a 155 mile bike trip and was pretty happy to be sitting there, not moving.

If you think that is close enough to "track your every move", your paranoia is your least problem. Also check his previous post on how this "tracking" goes way off track.

umm yes you can. By knowing the distance you are from a set of towers at specific times, I can tell exactly where you are.

So if you don't have that information, how hard is it then? Exactly. http://www.willclarke.net/?p=278

Take it as you will but this dude seems to think this data isn't actually a log of where an iPhone user has been. He claims it is actually location data of the cell towers the iPhone has seen. Obviously that kind of data could give rough location data but not with any granularity or meaningful accuracy.

I do have an iPhone and have looked at my own data with the Tracker app. On the surface I would have to say there is some validity to this guy's claim because the location data on my phone included places I haven't been within 10 or 20 miles of ever. With that said I still installed the untrack app on my phone to dump the tables in the database where this data is stored, but that's mainly because my Tinfoil Hat Wearer's Club membership agreement required me to do so.

It has meanwhile been debunked that this file tracks the location of the iPhone. It draws a map of locations of cell towers. The positions in this file are not the position of the iPhone when the user used a location app, the positions are the locations of the cell towers the iPhone saw in this moment. This is pretty clear now. The cell tower ID is the UNIQUE ID of the database, there are only clusters of tower locations saved at the same time with locations miles apart and NONE of these are the actual position of your phone.

Some real world testing: http://www.willclarke.net/?p=247

And yes, this also paints a rough picture of where you used location services, because only the stations around the places where you used location services are in this database. But: The stations are miles around your real position and since there is no signal strength info saved triangulation is not possible. I have found stations recorded that were up to ten miles away from my true position and hardly any stations nearer than half a mile (you'd need to stand right under a cell tower and use Google Maps there to have the position of the iPhone and the tower match by accident, so this happens almost never and the data shows exactly that).

So: The iPhone builds a local database with a network topography map and never throws it away. If it would throw that info away it would need to ask external databases (of Google or SkyHook) instead to learn the coordinates of the towers that it sees. By doing so it would neccessarily TELL these providers where it is.

Basically you have the choice of your phone tracking you (very roughly) in an internal database or have someone else providing an external database and by this tracking your phone. The iPhone does the first, Android does the latter (and Android even sends the Unique Device ID along). Believe it or not, but technically Jobs is right. The iPhone tracks you in an internal database, but with Android Google tracks your phone in external databases.

I don't expect many people to understand that though. Even with much explaining to basically neutral people hardly more than 5 of ten understand how positioning works and what it implies. Or what a "Unique Device ID" is.

It's only unencrypted on your computer if you don't encrypt your backups (which is a click away in iTunes).

But this is nothing new. I know people securing their computers very tightly and still without thinking store their backups unencrypted and unsecured. People...

And: http://www.willclarke.net/?p=247 -- This is not a database of where you've been, it's a database of cell towers your phone has seen, one entry per cell tower. Looking at the data on my iPhone I came to the same conclusion. I have found hardly any datapoint in there closer than half a mile to my real position and when I was on high ground in otherwise flat land the iPhone recorded dozens of locations at once from up to tens of miles around.

But now having a cell tower map of all areas I have been surely is nice! Thanks, Apple!

I found this via Hacker News.

willclarke.net - Apple is not “recording your moves”
http://www.willclarke.net/?p=247

Mr. Clarke's research implies that cell tower and Wi-Fi network locations are recorded, but phone location is *not* recorded, in the file at issue.

Of course, if you request the location of nearby restaurants via iPhone app, then your location is must be determined. I have seen no proof that user accessible *device* location data is stored.

If such data were available, why would an application like "Trails - GPS Tracker" ever need to "Resume recording"?

When looking at the data stored in that DB on my iPhone I came to exactly the same conclusion. The iPhone builds a local network topography map of cell towers and WiFi base stations to avoid having to look up that data over and over again from the databases at Google and SkyHook (as Android does it). Not more, not less.

And this is not only faster than accessing external databases and consumes less power, it also does NOT leak your location data to these service providers. Whenever a phone (or another device) asks an third party provider where a cell tower with a certain ID is, it also tells that provider where it is. So basically you have the choice of your phone tracking you (by drawing an internal map with coordinates of cell towers it has seen) or have someelse tracking your phone (by recording a map of cell towers your phone as seen).

Insisting in your phone not building up such a database so that nobody can steal it with your phone is like not hoarding your money at home in case a burglar finds it and instead giving the money to strangers in the street. Surely a wise move!

But try to explain that to people. I'm trying this since days and you have to talk so much that everyone shouting "OMG! Apple is spying on you and recording every move!!!" will get heard much easier. It's like trying to teach science to people jumping around a stake, burning a witch. Talk about germs versus curses then and you can count yourself lucky if you don't end up on the stake yourself.

Thanks very much for that link, by the way. This is one of the very few pieces of real work to analyse what's going on instead of just opinion and FUD. And it totally mirrors what I got when I had a closer look at that data.

"Apple's iPhone 3G, iPhone 3GS, the iPhone 4, and iPad models are keeping track of consumers whereabouts"

I found this via Hacker News.

willclarke.net - Apple is not “recording your moves”
http://www.willclarke.net/?p=247

Mr. Clarke's research implies that cell tower and Wi-Fi network locations are recorded, but phone location is *not* recorded, in the file at issue.

Of course, if you request the location of nearby restaurants via iPhone app, then your location is must be determined. I have seen no proof that user accessible *device* location data is stored.

If such data were available, why would an application like "Trails - GPS Tracker" ever need to "Resume recording"?