A way to track people with cellphones with GPS capabilities turned off

The novel part here appears to be doing shape matching against road maps to improve accuracy. The accelerometers and gyroscope in consumer devices are so inaccurate that any track will be mostly useless after a few minutes, but if they can periodically tie that data back to known map points then accuracy improves a lot.

I'd like to see navigation apps make use of this approach when then lose GNSS signals, like in a tunnel.

You can also be tracked via local wi-fi access points. Google has built a database mapping access points to GPS coordinates. All they need is access to wi-fi information and they can find your location even if you have GPS and 4G disabled. There is really little you can do nowadays to protect your privacy.

Bingo !

Can't you remove your battery?

Every baseband (cellular chip) is mandated closed sourced, and likely backdoored.

Open source basebands NOW.

The main point here is that they're doing the tracking with a typical user mode application without access to anything that a user would know is giving away their location.

Tracking location with other sensors requires more permissions.

Agreed, the title is very misleading.

Perhaps the author thinks "GPS" refers to the general problem of tracking location, rather than a specific system that solves that problem?

Yes, the title is wrong.

Maybe "How smartphones can track you, even when you turn GPS off"?

But also, these researchers apparently didn't have access to cell-tower location data. Or at least, it's not mentioned in the article.

Doubt the author - and most laypeople - understand how GPS works.

It is absolutely not "How GPS can track you, even when you turn it off". It's an article for the average consumer and the title should've been "how your location can be found even without GPS". This is just a clickbait-title.

Doing inertial navigation with the sensors only is not going to work well. In this invention they seem to augment the sensors with external information and deduce the most probable location that way - the article is rather scant on details though.

AFAIK you can be located using cell towers both on the device side and the cell network side.

You can be located with WIFI too: if you have WIFI enabled and communicate the access point names to Google/Apple, your location can be discovered. WIFI AP locations collected beforehand (by something like the Google car or the phone itself) are matched with their known accurate position and the measured AP signal strengths.

And Bluetooth beacons can also be used for location. What else... the pictures you take with the camera and upload to a cloud storage can be used to locate you.

Having a functioning inertial navigation would be very useful for many purposes. For example, offline navigation without GPS (=longer battery life).