Jiangchuan Zheng

Modelling heterogeneous location habits in human populations for location prediction under data sparsity

In recent years, researchers have sought to capture the daily life location behaviour of groups of people for exploratory, inference, and predictive purposes. However, development of such approaches has been limited by the requirement of personal semantic labels for locations or social/spatial overlap between individuals in the group. To address this shortcoming, we present a Bayesian model of mobility in populations (i.e., groups without spatial or social interconnections) that is not subject to any of these requirements. The model intelligently shares temporal parameters between people, but keeps the spatial parameters specific to individuals. To illustrate the advantages of population modelling, we apply our model to the difficult problem of overcoming data sparsity in location prediction systems, using the Nokia dataset comprising 38 individuals, and find a factor of 2.4 improvement in location prediction performance against a state-of-the-art model when training on only 20 hours of observations.

An unsupervised learning approach to social circles detection in ego bluetooth proximity network

Understanding a users social interactions in the physical world proves important in building context-aware ubiquitous applications. A good way towards that objective is to categorize people to whom a user is socially related into what we call as social circles. In this note, we propose a novel unsupervised approach that learns from the Bluetooth (BT) sensed data recording ones dynamic proximity relations with others to identify her social circles, each of which is formed along a semantically coherent aspect. For each circle we learn its members as well as the temporal dimensions along which it is formed. Our method is innovative in that it well overcomes data sparsity by information sharing, and allows for circle overlaps which is common in reality. Experiments on real data demonstrate the effectiveness of our method, and also show the potentials of relational mobile data in sensing personal behaviors beyond personal data.

Inferring Road Type in Crowdsourced Map Services

In crowdsourced map services, digital maps are created and updated manually by volunteered users. Existing service providers usually provide users with a feature-rich map editor to add, drop, and modify roads. To make the map data more useful for widely-used applications such as navigation systems and travel planning services, it is important to provide not only the topology of the road network and the shapes of the roads, but also the types of each road segment (e.g., highway, regular road, secondary way, etc.). To reduce the cost of manual map editing, it is desirable to generate proper recommendations for users to choose from or conduct further modifications. There are several recent works aimed at generating road shapes from large number of historical trajectories; while to the best of our knowledge, none of the existing works have addressed the problem of inferring road types from historical trajectories. In this paper, we propose a model-based approach to infer road types from taxis trajectories. We use a combined inference method based on stacked generalization, taking into account both the topology of the road network and the historical trajectories. The experiment results show that our approach can generate quality recommendations of road types for users to choose from.