> One test subject's commute across Seattle that the researchers tracked with ads in the app Talkatone. The dotted lines show the subject's real path, while the red dots show where the ads were delivered to the subject's phone to reveal his or her workplace, bus stop, home and local coffee shop. (The subject's actual home location has been somewhat obscured for privacy.)

It's not tracking across a bus path; that's their actual path. The red dots are the tracked locations.