  Unmanned aerial vehicle (UAV)-based visual object tracking has enabled a wide
range of applications and attracted increasing attention in the field of
intelligent transportation systems because of its versatility and
effectiveness. As an emerging force in the revolutionary trend of deep
learning, Siamese networks shine in UAV-based object tracking with their
promising balance of accuracy, robustness, and speed. Thanks to the development
of embedded processors and the gradual optimization of deep neural networks,
Siamese trackers receive extensive research and realize preliminary
combinations with UAVs. However, due to the UAV's limited onboard computational
resources and the complex real-world circumstances, aerial tracking with
Siamese networks still faces severe obstacles in many aspects. To further
explore the deployment of Siamese networks in UAV-based tracking, this work
presents a comprehensive review of leading-edge Siamese trackers, along with an
exhaustive UAV-specific analysis based on the evaluation using a typical UAV
onboard processor. Then, the onboard tests are conducted to validate the
feasibility and efficacy of representative Siamese trackers in real-world UAV
deployment. Furthermore, to better promote the development of the tracking
community, this work analyzes the limitations of existing Siamese trackers and
conducts additional experiments represented by low-illumination evaluations. In
the end, prospects for the development of Siamese tracking for UAV-based
intelligent transportation systems are deeply discussed. The unified framework
of leading-edge Siamese trackers, i.e., code library, and the results of their
experimental evaluations are available at
https://github.com/vision4robotics/SiameseTracking4UAV .
