Add to the towers triangulating data, there's a gyroscope(position of the phone), accelerometer, barometer(sensor of pressure = your altitude), wifi AP's signals triangulation which greatly enchances your location data. You can literally be seen walking up/down the stairs. Every single step. More. Scrolling through your FB feed tour camera tracking your eyes movement can basicaly think what exactly you're looking at/reading/skipping. Analyzing your patterns and comparing them to some control/average interactions with the help of AI you can basically be read throughout. Stay safe.