The use of location data has greatly benefited from the availability of location-based services, the popularity of social networks, and the accessibility of public location data sets. However, in addition to providing users with the ability to obtain accurate driving directions or the convenience of geo-tagging friends and pictures, location is also a very sensitive type of data, as attested by more than a decade of research on different aspects of privacy related to location data.
In this chapter, we focus on two domains that rely on location data as their core component: Geospatial applications (such as thematic maps and crowdsourced geo-information) and location-based social networks. We discuss the increasing relevance of geospatial applications to the current location-aware services, and we describe relevant concepts such as volunteered geographic information, geo-surveillance and how they relate to privacy. Then, we focus on a subcategory of geospatial applications, location-based social networks, and we introduce the different entities (such as users, services and providers) that are involved in such networks, and we characterize their role and interactions. We present the main privacy challenges and we discuss the approaches that have been proposed to mitigate privacy risks in location-based social networks. Finally, we conclude with a discussion of open research questions and promising directions that will contribute to improve privacy for users of location-based social networks.