There is a contradiction at the heart of our current understanding of individual and collective mobility patterns. On one hand, a highly influential stream of literature on human mobility driven by analyses of massive empirical datasets finds that hu
man movements show no evidence of characteristic spatial scales. There, human mobility is described as scale-free. On the other hand, in geography, the concept of scale, referring to meaningful levels of description from individual buildings through neighborhoods, cities, regions, and countries, is central for the description of various aspects of human behavior such as socio-economic interactions, or political and cultural dynamics. Here, we resolve this apparent paradox by showing that day-to-day human mobility does indeed contain meaningful scales, corresponding to spatial containers restricting mobility behavior. The scale-free results arise from aggregating displacements across containers. We present a simple model, which given a persons trajectory, infers their neighborhoods, cities, and so on, as well as the sizes of these geographical containers. We find that the containers characterizing the trajectories of more than 700,000 individuals do indeed have typical sizes. We show that our model generates highly realistic trajectories without overfitting and provides a new lens through which to understand the differences in mobility behaviour across countries, gender groups, and urban-rural areas.
Data-driven research in mobility has prospered in recent years, providing solutions to real-world challenges including forecasting epidemics and planning transportation. These advancements were facilitated by computational tools enabling the analysis
of large-scale data-sets of digital traces. One of the challenges when pre-processing spatial trajectories is the so-called stop location detection, that entails the reduction of raw time series to sequences of destinations where an individual was stationary. The most widely adopted solution to this problem was proposed by Hariharan and Toyama (2004) and involves filtering out non-stationary measurements, then applying agglomerative clustering on the stationary points. This state-of-the-art solution, however, suffers of two limitations: (i) frequently visited places located very close (such as adjacent buildings) are likely to be merged into a unique location, due to inherent measurement noise, (ii) traces for multiple users can not be analysed simultaneously, thus the definition of destination is not shared across users. In this paper, we describe the Infostop algorithm that overcomes the limitations of the state-of-the-art solution by leveraging the flow-based network community detection algorithm Infomap. We test Infostop for a population of $sim 1000$ individuals with highly overlapping mobility. We show that the size of locations detected by Infostop saturates for increasing number of users and that time complexity grows slower than for previous solutions. We demonstrate that Infostop can be used to easily infer social meetings. Finally, we provide an open-source implementation of Infostop, written in Python and C++, that has a simple API and can be used both for labeling time-ordered coordinate sequences (GPS or otherwise), and unordered sets of spatial points.
