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January 28, 2021

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Cassia Artanegara

Should I let my phone collect my location once, while in-use, or all the time?

Illustration for Should I let my phone collect my location once, while in-use, or all the time?

It’s probably not news to you that our phones can track our locations and share them with third party entities. But what exact information about our location is being tracked and shared, and what does that information reveal about us and our lives? This article demystifies three different types of mobile location tracking: single location data points, one-off traces, and persistent location tracking.

One time access, right now: a single location data point
When an app has permission to collect your location once, the app can get precise GPS coordinates for where the device is at that moment.

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To give an example, a single data point, Point A, could reveal that Jane’s phone (and since most of us are attached to our phones at the hip, we can assume Jane herself) was at GPS coordinate 38.8976997, -77.0365532 on January 4, 2021 at 10:28 AM. The app might be able to infer the location and why Jane was there, but the app won’t know the significance of the location: does Jane live there or nearby, is she on vacation from out of town, or is she in the midst of an out-of-the-ordinary trip? In other words, a limited amount of information is available based on one location point and timestamp.

What are the implications?
It depends on where you were, which app you were using, and how you feel about creating a record that you visited the location. Were you at a grocery store? Were you where you work? Were you at a health clinic? Were you at your house? Which app were you using? Do you want that app to have a record that you were at that place?

One-off traces
A one-off trace would poll and record Jane’s phone’s location over a finite period of time while the app is actively being used (in the foreground, that is: the app that you have open at the moment). An example would be a running app that tracks Jane’s location while out on a run so she knows how far she ran.

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Some mobile devices use a blue bar at the top of the screen to communicate that a one-off trace is happening. With this information, whoever collected the data would know the route Jane followed, how long it took her to complete this route (and could further deduce perhaps, the mode of her transportation), whether the speed at which she completed it was slower or faster than the average speed of completion, etc.

What are the implications?
It depends on which app you’re using, how often you use it, and where you’re going when you use it. The app could learn quite a bit about your habits and the areas you frequent and use that information to make inferences about who you are.

Persistent location tracking
When an app has permission to collect the device’s location at any time, the app can poll the location at ANY time; for some apps, this means ALL the time. A report by the New York Times discovered that some apps poll location data as often as every 2 seconds (totaling 172,800 collection points over the course of just one day!). If you carry your phone with you at all times and an app has access to this permission, it can sample your location at any time until you revoke it. And because persistent tracking occurs all the time, location can be tracked whether or not the app is in use. You might not even expect or realize your location is being tracked in the background (i.e., when the app is not in use).

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A wealth of data points might come together over time to contextualize each point within a narrative about that person: in a one off trace, Jane’s two mile trip appears to be an innocuous trip around the city. Add in the rest of the data points and that particular trip suddenly stands out against the pattern of Jane’s location habits.

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Layering in even the simplest of data from a user’s location history — in this case, categorizing the trips into ones that occurred on the weekend and ones that occurred on a weekday — provides even more context for Jane’s unusual trip. What could have possibly led Jane to travel so far from her normal weekday paths? A motivated analyst could combine this information with publicly available information, like the businesses and destinations in that area that were open at the time she made her trip, to guess that she went to an oncologist appointment — information that could be quite dangerous in the hands of the wrong people.

What are the implications?
Most people probably aren’t expecting to be tracked or to have their habits analyzed for meaning or used for predicting next steps. It can be disconcerting to think that this information is being collected and used without our knowledge. Be judicious about which apps you allow access to your location and ask yourself, “Does the app provide value to me based on knowing where I am?” If you have an Android read this. If you have an iPhone read this.

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The more location data you allow an app to collect, the more information companies can extract and deduce about you.

Related questions

What’s location data?

Our smartphones, and many other devices, are GPS-enabled. That means they can communicate with the GPS satellites all around us to get the coordinates of the device’s location when needed. If you have a mobile phone, you might use location-enabled features like searching for a grocery store nearby.