  Localization and tracking are two very active areas of research for robotics,
automation, and the Internet-of-Things. Accurate tracking for a large number of
devices usually requires deployment of substantial infrastructure (infrared
tracking systems, cameras, wireless antennas, etc.), which is not ideal for
inaccessible or protected environments. This paper stems from the challenge
posed such environments: cover a large number of units spread over a large
number of small rooms, with minimal required localization infrastructure. The
idea is to accurately track the position of handheld devices or mobile robots,
without interfering with its architecture. Using Ultra-Wide Band (UWB) devices,
we leveraged our expertise in distributed and collaborative robotic systems to
develop an novel solution requiring a minimal number of fixed anchors. We
discuss a strategy to share the UWB network together with an Extended Kalman
filter derivation to collaboratively locate and track UWB-equipped devices, and
show results from our experimental campaign tracking visitors in the Chambord
castle in France.
