ABSTRACT Motion estimation (ME) being a fundamental process of crowd behavior analysis experienced real challenges at high densities due to visual ambiguities and occlusion problems etc. Various surveys reported in the past years summarize conventional ME methods for crowd behaviors at low/medium densities. In this paper, we focus on state-of-the-art fluid dynamics (FD) ME methods developed over the last one and the half-decade for high-density crowd analysis. A detailed discussion is provided on the development of FD ME methods explaining the strengths and weaknesses and viability of FD ME methods for anomaly detection at high crowd densities. Comprehensive experiments are performed comparing the performance of conventional and FD ME at varying crowd densities. Experimentation results show that conventional ME methods fail at high-density crowd whereas FD ME methods could estimate motion only at the global level. Still, research is required to meet the challenges of local ME at high crowd densities.

中文翻译：

---

基于流体动力学的高密度人群运动估计

摘要 由于视觉模糊和遮挡问题等，运动估计 (ME) 作为人群行为分析的基本过程在高密度下遇到了真正的挑战。 过去几年报告的各种调查总结了低/中密度人群行为的传统 ME 方法。在本文中，我们专注于在过去五年和过去五年中为高密度人群分析开发的最先进的流体动力学 (FD) ME 方法。详细讨论了 FD ME 方法的发展，解释了 FD ME 方法在高人群密度下进行异常检测的优缺点和可行性。进行了综合实验，比较了传统和 FD ME 在不同人群密度下的性能。实验结果表明，传统的 ME 方法在高密度人群中失败，而 FD ME 方法只能在全局级别估计运动。尽管如此，仍需要研究以应对高人群密度下本地 ME 的挑战。