Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: UAV-based Crowd Surveillance in Post COVID-19 Era   To cope with the current pandemic situation and reinstate pseudo-normal daily
life, several measures have been deployed and maintained, such as mask wearing,
social distancing, hands sanitizing, etc. Since outdoor cultural events,
concerts, and picnics, are gradually allowed, a close monitoring of the crowd
activity is needed to avoid undesired contact and disease transmission. In this
context, intelligent unmanned aerial vehicles (UAVs) can be occasionally
deployed to ensure the surveillance of these activities, that health
restriction measures are applied, and to trigger alerts when the latter are not
respected. Consequently, we propose in this paper a complete UAV framework for
intelligent monitoring of post COVID-19 outdoor activities. Specifically, we
propose a three steps approach. In the first step, captured images by a UAV are
analyzed using machine learning to detect and locate individuals. The second
step consists of a novel coordinates mapping approach to evaluate distances
among individuals, then cluster them, while the third step provides an
energy-efficient and/or reliable UAV trajectory to inspect clusters for
restrictions violation such as mask wearing. Obtained results provide the
following insights: 1) Efficient detection of individuals depends on the angle
from which the image was captured, 2) coordinates mapping is very sensitive to
the estimation error in individuals' bounding boxes, and 3) UAV trajectory
design algorithm 2-Opt is recommended for practical real-time deployments due
to its low-complexity and near-optimal performance.

4
The categories of this paper are: cond-mat
3
The categories of this paper are: physics
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
2
The categories of this paper are: math
24
The categories of this paper are: dg-ga
15
The categories of this paper are: nucl-ex
21
The categories of this paper are: adap-org
25
The categories of this paper are: patt-sol
37
The categories of this paper are: supr-con
23
The categories of this paper are: solv-int
22
The categories of this paper are: chao-dyn
28
The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
35
The categories of this paper are: mtrl-th