A digital equivalent to the fictional Harry Potter’s ‘Marauder’s Map’ can pinpoint your friends’ locations using information from Facebook (illustrated). The extension loads when the Messages tab is opened and ‘scrapes’ the page for location data to show the movement of friends with a startling degree of accuracy
Aran Khanna, a Computer Science and Mathematics student at Harvard, came up with the map to explore how much data Messenger was revealing to people he chatted to.
The Messenger app lets people send their location to friends and it defaults to sending a location with all messages.
By trawling through his Messenger history, Mr Khanna noticed the latitude and longitude coordinates of the message locations have more than five decimal places of precision, meaning that a sender’s location is pinpointed to within three feet (one metre).
He shared this discovery in a post for Medium.com.
He then wrote a Chrome extension for the Facebook Messenger page that takes this location data and plots it on a map.