If you visit [beer-rating app] Untappd venue locations through the web rather than the app, they will list “loyal patrons,” the top 15 users that have checked in most frequently at that location. These are perfect candidates to piggyback on, as they are both likely to have a strong connection to that location, and be active users that will be checking in elsewhere as well. This allows us to map connections between locations.
For example, by examining users that are “loyal patrons” of Dutch military locations (light blue) and identifying the other military locations (red) they have visited, we can begin to map out possible Dutch military connections across the globe, including locations of military exercises and missions
By comparing the location history of several different users, it also becomes possible to identify non-military locations that they have in common.