Recent years have seen an unprecedented spread of Unmanned Aerial Vehicles (UAVs, or “drones”), which are highly useful for both civilian and military applications. Flight safety is a crucial issue in UAV navigation, having to ensure accurate compliance with recently legislated rules and regulations. The emerging use of autonomous drones and UAV swarms raises additional issues, making it necessary to transfuse safety- and regulations-awareness to relevant algorithms and architectures. Computer vision plays a pivotal role in such autonomous functionalities. Although the main aspects of autonomous UAV technologies (e.g., path planning, navigation control, landing control, mapping and localization, target detection/tracking) are already mature and well-covered, ensuring safe flying in the vicinity of crowds, avoidance of passing over persons, or guaranteed emergency landing capabilities in case of malfunctions, are generally treated as an afterthought when designing autonomous UAV platforms for unstructured environments. This fact is reflected in the fragmentary coverage of the above issues in current literature. This overview attempts to remedy this situation, from the point of view of computer vision. It examines the field from multiple aspects, including regulations across the world and relevant current technologies. Finally, since very few attempts have been made so far towards a complete UAV safety flight and landing pipeline, an example computer vision-based UAV flight safety pipeline is introduced, taking into account all issues present in current autonomous drones. The content is relevant to any kind of autonomous drone flight (e.g., for movie/TV production, news-gathering, search and rescue, surveillance, inspection, mapping, wildlife monitoring, crowd monitoring/management), making this a topic of broad interest.

中文翻译：

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用于自主无人机飞行安全的计算机视觉：概述和基于视觉的安全着陆管道示例

近年来，无人驾驶飞行器（UAV，或“无人机”）空前普及，对民用和军用应用都非常有用。飞行安全是无人机导航中的一个关键问题，必须确保准确遵守最近制定的法规。自主无人机和无人机群的新兴使用引发了其他问题，因此有必要将安全和法规意识注入相关算法和架构。计算机视觉在这种自主功能中发挥着关键作用。虽然自主无人机技术的主要方面（如路径规划、导航控制、着陆控制、测绘与定位、目标检测/跟踪）已经成熟且覆盖面广，确保在人群附近安全飞行，避免超车人，在为非结构化环境设计自主无人机平台时，通常会考虑在发生故障时保证紧急着陆能力。这一事实反映在当前文献对上述问题的零散报道中。本概述试图从计算机视觉的角度纠正这种情况。它从多个方面审视该领域，包括世界各地的法规和相关的当前技术。最后，由于迄今为止很少有人尝试建立完整的无人机安全飞行和着陆管道，因此介绍了一个基于计算机视觉的无人机飞行安全管道示例，同时考虑了当前自主无人机中存在的所有问题。内容与任何类型的自主无人机飞行相关（例如，用于电影/电视制作、新闻采集、