  In the study "Spatio-temporal Gaussian process models for extended and group
object tracking with irregular shapes" (IEEE Trans. Veh. Tech., vol. 68, no. 3,
pp. 2137-2151, Mar. 2019), the extended object tracking problem was tackled by
an approach based on spatio-temporal Gaussian processes (STGP). The performance
of the proposed STGP-based trackers was comparatively evaluated through
simulations and real data together with another state-of-the-art method
(referred to as GP-EKF) proposed in "Extended target tracking using Gaussian
processes" (IEEE Trans. Signal Process., vol. 63, no. 16, pp. 4165-4178, Aug.
2015). Unfortunately, we recognized that there are major errors in the
implementation of the experiments presented in the STGP paper, which led to
incorrect performance evaluation results. In this correspondence, our aim is to
share the correct results of these experiments and to respond to some claims
regarding GP-EKF, which we believe, would contribute to a better understanding
of the methods.
