  Ultra-wideband (UWB) wireless technology has seen an increased penetration in
the robotics field as a robust localization method in recent years. UWB enables
high accuracy distance estimation from time-of-flight measurements of wireless
signals, even in non-line-of-sight measurements. UWB-based localization systems
have been utilized in various types of GNSS-denied environments for ground or
aerial autonomous robots. However, most of the existing solutions rely on a
fixed and well-calibrated set of UWB nodes, or anchors, to estimate accurately
the position of other mobile nodes, or tags, through multilateration. This
limits the applicability of such systems for dynamic and ad-hoc deployments,
such as post-disaster scenarios where the UWB anchors could be mounted on
mobile robots to aid the navigation of UAVs or other robots. We introduce a
collaborative algorithm for online autocalibration of anchor positions,
enabling not only ad-hoc deployments but also movable anchors, based on
Decawave's DWM1001 UWB module. Compared to the built-in autocalibration process
from Decawave, we drastically reduce the amount of calibration time and
increase the accuracy at the same time. We provide both experimental
measurements and simulation results to demonstrate the usability of this
algorithm.
