“…Transmitting and storing raw trajectory data consumes too much network bandwidth and storage capacity [2, 5, 15-17, 20, 22-24, 27, 34]. It is known that these issues can be resolved or greatly alleviated by trajectory compression techniques via removing redundant data points of trajectories [2,4,5,7,10,12,[15][16][17][18]20,23,24,27], among which the piece-wise line simplification technique is widely used [2, 4, 5, 7, 15-17, 20, 23], due to its distinct advantages: (a) simple and easy to implement, (b) no need of extra knowledge and suitable for freely moving objects, and (c) bounded errors with good compression ratios [15,27].…”