  During missions involving radiation exposure, unmanned robotic platforms may
embody a valuable tool, especially thanks to their capability of replacing
human operators in certain tasks to eliminate the health risks associated with
such an environment. Moreover, rapid development of the technology allows us to
increase the automation rate, making the human operator generally less
important within the entire process. This article presents a multi-robotic
system designed for highly automated radiation mapping and source localization.
Our approach includes a three-phase procedure comprising sequential deployment
of two diverse platforms, namely, an unmanned aircraft system (UAS) and an
unmanned ground vehicle (UGV), to perform aerial photogrammetry, aerial
radiation mapping, and terrestrial radiation mapping. The central idea is to
produce a sparse dose rate map of the entire study site via the UAS and,
subsequently, to perform detailed UGV-based mapping in limited
radiation-contaminated regions. To accomplish these tasks, we designed numerous
methods and data processing algorithms to facilitate, for example, digital
elevation model (DEM)-based terrain following for the UAS, automatic selection
of the regions of interest, obstacle map-based UGV trajectory planning, and
source localization. The overall usability of the multi-robotic system was
demonstrated by means of a one-day, authentic experiment, namely, a fictitious
car accident including the loss of several radiation sources. The ability of
the system to localize radiation hotspots and individual sources has been
verified.
