In the past five years, mapping of violence and disasters as they unfold, through various technologies, has emerged as a new way to observe and shape crises. Many mapping efforts rely on observations submitted by the “crowd”—a large, loose array of individuals and organizations, often in an online community, acting largely independent of one another to supply information in a distributed fashion. Disaster-affected communities are increasingly the source of Big (Crisis) Data, which they post and share on social media platforms like Twitter. Crowdsourcing the collection of crisis information from this user-generated content has evolved into a powerful and flexible way to detect and document crises in real time and real space. What this means is measurement of the characteristics of crisis situations as events are actually unfolding and at a geographical resolution that facilitates informed, prompt, and targeted decision making. Naturally, the availability of real-time and real-space data has important implications for conceiving, designing, and implementing interventions during crises, which can be more rapid and effective as a consequence.