  The combination of ultrawideband (UWB) radios and inertial measurement units
(IMU) can provide accurate positioning. To ensure reliable communication, the
radios are generally mounted at the extremities of a mobile system whereas the
IMUs are located closer to the center of gravity for use in control, resulting
in a spatial offset between the IMU and the UWB radio. Additionally, data from
heterogeneous sensors can arrive at different time instants. The systematic
fusion of data from multiple sources requires the temporal offset and spatial
offset between the sensors to be known. An important aspect of calibration is
the observability of the system state and identifiability of the system
parameters. Estimating the state or parameters of a system that is otherwise
unobservable or unidentifiable, can result in poor estimates. In this report,
the local weak observability of the state and the identifiability of the
temporal offset for a tightly-coupled UWB-aided inertial localization system is
studied.
