The aim of this Vehicle-Infrastructure-Air Cross-Domain Collaborative Perception Algorithm Competition is to significantly enhance the environmental perception capabilities of intelligent unmanned systems in intricate, highly dynamic, and unstructured road scenarios.  Participants in this challenge must create clever algorithms for effective cross-domain data fusion and collaborative perception.  Multi-source, heterogeneous data from connected-autonomous vehicles, mobile roadside infrastructure units, and aerial platforms must be integrated into these algorithms.  The objective is to accomplish cross-domain data fusion and collaborative perception in complicated settings by overcoming the constraints of single-platform perception.  In the end, this will give autonomous unmanned systems stronger assistance for job planning and wise decision-making by improving their environmental sensing capabilities.