With the growing concerns over public safety, the importance of crowd monitoring is being realized by various security and event management agencies worldwide. Estimation of crowd dynamics can help such agencies in the prevention of any unanticipated accidents or issues. Research on crowd monitoring has been underway since the past few decades. Conventional crowd monitoring systems mainly rely on computer vision approach. Due to predominant use of videos/ image sequences, the existing techniques may raise data privacy concerns. This has led to the development of new crowd monitoring techniques which are privacy-preserving and require minimum public participation. This paper aims to serve as a single and sufficient source of information to the concerned researchers on various aspects of crowd monitoring and also provide future directions which can be helpful in developing advanced crowd monitoring techniques.

随着对公共安全的日益关注，世界各地的各种安全和事件管理机构都意识到人群监控的重要性。人群动态的估计可以帮助这些机构预防任何意外事故或问题。自过去几十年以来，人们一直在进行人群监测的研究。传统的人群监控系统主要依靠计算机视觉方法。由于主要使用视频/图像序列，现有技术可能会引起数据隐私问题。这导致了新的人群监控技术的发展，这些技术可以保护隐私并且需要最少的公众参与。