Online Calibration for Networked Radar Tracking of UAS

The need for effective tracking mechanisms of small unmanned aircraft systems (sUAS) has become crucial as their use has increased in populated areas. This paper presents a practical tracking solution for sUAS using a network of phased array radars. Achieving optimal system performance while tracking the sUAS requires extrinsic calibration of the individual radar systems to a common frame of reference. We propose a straightforward calibration solution based upon the orthogonal Procrustes formulation that uses radar measurements from ground-mounted radar associated with real-time-kinematic global positioning system (RTK-GPS) data. Two variations of the calibration are provided: a batch processing method, and an online method for real-time adjustments. This paper provides a practical analysis of the advantages and disadvantages associated with both calibration methods. This assessment of the calibration methods, along with an evaluation of the radar network's sUAS tracking ability, is validated by simulation studies and hardware tests. The hardware experiments especially provide valuable insights into the practical implications of the proposed tracking solution.