  Ultra-wideband technology has emerged in recent years as a robust solution
for localization in GNSS denied environments. In particular, its high accuracy
when compared to other wireless localization solutions is enabling a wider
range of collaborative and multi-robot application scenarios, being able to
replace more complex and expensive motion-capture areas for use cases where
accuracy in the order of tens of centimeters is sufficient. We present the
first survey of UWB-based localization focused on multi-UAV systems and
heterogeneous multi-robot systems. We have found that previous literature
reviews do not consider in-depth the challenges in both aerial navigation and
navigation with multiple robots, but also in terms of heterogeneous multi-robot
systems. In particular, this is, to the best of our knowledge, the first survey
to review recent advances in UWB-based (i) methods that enable ad-hoc and
dynamic deployments; (ii) collaborative localization techniques; and (iii)
cooperative sensing and cooperative maneuvers such as UAV docking on mobile
platforms. Finally, we also review existing datasets and discuss the potential
of this technology for both localization in GNSS-denied environments and
collaboration in multi-robot systems.
