  In emergency situations, actions that save lives and limit the impact of
hazards are crucial. In order to act, situational awareness is needed to decide
what to do. Geolocalized photos and video of the situations as they evolve can
be crucial in better understanding them and making decisions faster. Cameras
are almost everywhere these days, either in terms of smartphones, installed
CCTV cameras, UAVs or others. However, this poses challenges in big data and
information overflow. Moreover, most of the time there are no disasters at any
given location, so humans aiming to detect sudden situations may not be as
alert as needed at any point in time. Consequently, computer vision tools can
be an excellent decision support. The number of emergencies where computer
vision tools has been considered or used is very wide, and there is a great
overlap across related emergency research. Researchers tend to focus on
state-of-the-art systems that cover the same emergency as they are studying,
obviating important research in other fields. In order to unveil this overlap,
the survey is divided along four main axes: the types of emergencies that have
been studied in computer vision, the objective that the algorithms can address,
the type of hardware needed and the algorithms used. Therefore, this review
provides a broad overview of the progress of computer vision covering all sorts
of emergencies.
