Figure 2. Criteria for extracting trips.
(a) Two steps for extracting trips from one individual check-in trajectory. A1A2A3A4A5A6… is one individual trajectory sequence. (b) The demonstration of applying the criterions into the anonymous individuals' trajectories. The blue line is the original check-in trajectory. When segmenting this trajectory to trips, we filter the successive check-in pairs that the speed is faster than 431 km/h, such as A3->A4 and A7->A8; or time interval is greater than 12 hours, such as A2->A3 and A9->A10; or the displacement is less than 100 m, such as A4->A5.