The 4th JRC ECML Crisis Management Technology Workshop on Unmanned Aerial Systems for Rapid Mapping was co-organised by the European Commission Joint Research Centre and the United Nations Institute for Training and Research - Operational Satellite Applications Programme (UNITAR - UNOSAT). It took place in Geneva & Dardagny, Switzerland from 11 to 13 September 2013. 74 participants from UN and EC stakeholders, NGOs, civil protection bodies, academia, and industry attended the workshop. The workshop's purpose was to present, demonstrate, and explore the state-of-the-art and future potential of unmanned aerial systems for rapid mapping applications in the context of humanitarian crisis aid and natural disaster relief operations. Main impressions from the workshop were the diversity in technological solutions for various practical uses, the rapid turnaround time from flight to having usable data at hand in the field and a reality check on what are still challenges related to flight permissions. Within the European Union a process on the harmonisation of the diverse regulations for UAS operations and the introduction of UAS into the civil airspace is ongoing. The UAS technology will most likely make a large impact on data collection in future emergency situations. In addition, based on what was demonstrated, the tools are also useful for disaster risk reduction activities.