Google’s Sensorvault is a location history database that police can query to see phones near the location of a crime. Google is the only company with such a database—and innocent people have been arrested because of it.

How Does Sensorvault Work?

According to a New York Times investigation, Sensorvault works using Location History. This is included on Android and is part of some Google apps for the iPhone. It’s not enabled by default, but there’s a good chance you’ve been asked to turn it on and have done so.

If you have location history enabled, Google stores a timeline of your movements—using your smartphone’s GPS and/or location information from your computer—and makes it available to you as part of your Google account online. You can go back and see your travels on a given day. Google can use this information to better tailor search results and recommendations to you. Google says it doesn’t share this data with advertisers or other companies.

Google gathers that location history data you’ve provided into a database named “Sensorvault,” and law enforcement can query it with a warrant:

For years, police detectives have given Google warrants seeking location data tied to specific users’ accounts. But the new warrants, often called “geofence” requests, instead specify an area near a crime. Google looks in Sensorvault for any devices that were there at the right time and provides that information to the police. Google first labels the devices with anonymous ID numbers, and detectives look at locations and movement patterns to see if any appear relevant to the crime. Once they narrow the field to a few devices, Google reveals information such as names and email addresses.

Google says this database wasn’t made for law enforcement purposes, but law enforcement has certainly seized on it. While Google is collecting other location data, Google told The New York Times that only location data from the “Location history” feature is stored in Sensorvault and other location data is stored in a different database.

In theory, this other database could be tapped with a warrant, too. The other location database might be much less useful than the Sensorvault database—and we haven’t seen any reports it’s been accessed.

Should You Care?

Whether you care about this is a personal decision. The New York Times investigation provides some powerful reasons you might want to care. Sure, you’re a law-abiding citizen—but you might end up near a crime. Do you want the cops to be investigating you because you happened to be in the wrong place at the wrong time?

And, realistically, you don’t have to make much of a change to get your location history data out of Google’s Sensorvault. You can keep using Google Maps and other Google services—they’ll just be a bit less personalized after you disable Google’s location history service.

On the other hand, this location history data does provide some nice personalization features in your Google account—and sure, if you’re a law-abiding citizen, you probably won’t get accidentally swept up in an investigation. Whether you want to enable or disable this feature is up to you.

What About Apple or Cellular Carriers?

For now, this sort of dragnet seems unique to Google, thanks to Google’s trove of location data and this database:

Investigators who spoke with The New York Times said they had not sent geofence warrants to companies other than Google, and Apple said it did not have the ability to perform those searches. Google would not provide details on Sensorvault, but Aaron Edens, an intelligence analyst with the sheriff’s office in San Mateo County, Calif., who has examined data from hundreds of phones, said most Android devices and some iPhones he had seen had this data available from Google.

It’s worth noting that, even if Google backs down and Apple still refuses to participate, your cellular carrier has information about your movements thanks to cellular tower connection data.

Law enforcement is likely working with Google because these cellular carriers don’t have a convenient database to track and easily query this data. We wouldn’t be surprised if, in a few years, cellular carriers were tracking this information and making it available to law enforcement in a similar way.

For now, it seems that Google’s location history is the only service that could potentially result in you getting swept up in an investigation just because you were near a location at a particular date and time.

How to Remove Your Location Data From Sensorvault

Only data associated with Google’s location history feature appears in the vault. So, if you don’t use location history, you’re good.

On an iPhone, your phone won’t be sending this location history data to Google unless you’ve installed Google apps—like Google Maps, for example—and enabled the location history feature. Of course, many people have.

To check whether location history is enabled, head to the Activity History page on Google’s website and sign in with the same Google account you use on your phone. You can click the arrow next to “Devices on this account” to see which devices you own are reporting location history information to Google.

If you’re not at a PC, you can also disable location history from your Android phone. On Android you can head to the buried Settings > Google > Google Account > Data & personalization > Activity Controls > Location History > Manage Settings screen.

To disable location history altogether, disable the “Location History” slider here. This will “Pause” location history collection from all your devices. Already collected data will still be saved in your Google account and you can resume collection whenever you like.

To delete your data, you’ll have to head to the Timeline page—you can click the “Manage Activity” link on the Activity History page to open it. This interface will also show you all the historical location history data you’ve shared with Google and let you look through it. Google introduced the location history feature in 2009, so there could be a decade worth of data here. Google keeps your location history forever—until you delete it.

To delete the location history data, click the gear at the bottom right corner of the page and select “Delete all Location History.”

Remember to repeat this step if you have multiple Google accounts and you want to disable location history for all of them.

This is all based on an excellent New York Times piece, and we encourage you to read it for more context. We’re just explaining the technical bits, but the New York Times will take you through all the other details.