Characterizing human mobility patterns is essential for understanding human behaviors and the interactions with socioeconomic and natural environment, and plays a critical role in public health, urban planning, transportation engineering and related fields. With the widespread of location-aware mobile devices and continuing advancement of Web 2.0 technologies, location-based social media (LBSM) have been gaining widespread popularity in the past few years. With an access to locations of hundreds of million users, profiles and the contents of the social media posts, the LBSM data provided a novel modality of data source for human mobility study. By exploiting the explicit location footprints and mining the latent demographic information implied in the LBSM data, the purpose of this paper is to investigate the spatiotemporal characteristics of human mobility with a particular focus on the impact of demography. To serve this purpose, we first collect geo-tagged Twitter feeds posted in the conterminous United States area, and organize the collection of feeds using the concept of space-time trajectory corresponding to each Twitter user. Commonly human mobility measures, including detected home and activity centers, are derived for each user trajectory. We then select a subset of Twitter users that have detected home locations in the city of Chicago as a case study, and apply name analysis to the names provided in user profiles to learn the implicit demographic information of Twitter users, including race/ethnicity, gender and age. Finally we explore the spatiotemporal distribution and mobility characteristics of Chicago Twitter users, and investigate the demographic impact by comparing the differences across three demographic dimensions (race/ethnicity, gender and age). We found that, although the human mobility measures of different demographic groups generally follow the generic laws (e.g., power law distribution), the demographic information, particular the race/ethnicity group, significantly affects the urban human mobility patterns.

Humans spend most of their life in indoor spaces. As indoor spaces are becoming increasingly complex, there are compelling needs for efficient indoor GIS and navigation systems. For indoor navigations, numerous geometric network models have been proposed as navigable spatial models for 3D indoor environments in the past decade. Most of the existing discussions, however, tend to focus on conceptual representations of geometric networks; not enough attention has been given on the generation processes of navigable networks for 3D indoor environments. It is actually nontrivial, considering accurate and complete floor plans, the conventional data sources for building indoor geometric networks, are oftentimes not available for various reasons (e.g., copyright, public safety concerns). With the continue advances of 3D imaging and scanning technologies, 3D data models with fine geometric structures and high quality textures are increasingly available for indoor spaces, thus provide a novel data source for building indoor geometric networks. In this paper, an interactive approach is presented to derive 3D, navigable, geometric network models from these 3D data models. Specifically, this approach includes three steps: decomposing 3D building models in terms of floors, interactively creating geometric network elements (e.g., nodes and edges) and then automatically generating geometric network models. The presented approach is implemented and its advantages are demonstrated with a real world 3D building data.