I. Introduction
Cross-domain unmanned systems are organic entities composed of multiple sets of unmanned systems with significant functional differences operating in different spatial domains. They can complementarily utilize various capabilities in different fields, enhancing efficiency and establishing advantages in multiple domains. Such systems have broad applications in military, counterterrorism, riot control, disaster relief, and other fields. However, it is challenging to achieve consistent representation, abstraction, and fusion of information with differences in perspectives, types, scales, and noise acquired by cross-domain platforms. Also, the large-scale environments cause difficulties in information storage and retrieval for traditional visual simultaneous localization and mapping (SLAM) system [1], [2], [3].