Non-intrusive methods for crowd estimation
- Publication Type:
- Thesis
- Issue Date:
- 2019
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Urban living and its vibration environment pose ever-increasing challenges in our everyday lives. Urban planning and managing events requires correct and accurate information about the city and its environment. Residents as an inseparable component of the urban environment are affected most by any changes to it. Furthermore, the daily interactions of residents put increasing pressure on road infrastructure, power supply, and environmental management, including water, noise, air quality, healthcare and safety. Therefore, understanding their behaviour and the ability to monitor changes is one of the main interests for city management groups.
Current crowd density estimation technologies that leverage IR depth perception and video and image processing have privacy and deployment issues. Non-intrusive solutions have been introduced to reduce computational expenses and concerns regarding the privacy of residents. Probing for available Bluetooth and probing for available WiFi devices are among the popular non-intrusive methods for crowd detection, crowd distribution analysis and behaviour monitoring. However, both methods are highly dependent on the availability of such devices. Moreover, the uniqueness of MAC addresses threatens the privacy of individuals.
Estimating the crowd density based on available electromagnetic (EM) energy-level measurements is a fully non-intrusive method that monitors variation in EM radiation within an environment using a combination of advanced metamaterials and analytics to create a crowd density estimation detector. When measuring the EM energy in an environment, any object introduced into the measured environment directly affects the amount of EM energy observed within the environment. The human body is on average 60% water, which has an effect on the amount of EM radiation within the environment. Measuring the effects of humans on the current environment and comparing with expected models of behaviour allow for an approximation of the number of individuals to be determined.
To accurately monitor changes in the EM energy observed, we make use of metamaterials. Metamaterials respond to various frequencies in terms of transmission, reflection and absorption. This feature provides the opportunity to use them as sensors in different applications. In this study, a polarization insensitive metamaterial absorber with size of 18 x 18 x 1:75mm³ is used to accurately measure variations in the signal levels at 2.4 GHz and 5.1 GHz. The absorbed energy is translated to measurable parameters of voltage and current through a network of resistors. The level of absorbed energy varies with the introduction of any absorbing object which can be detected by monitoring available voltage and current values. Simulation and measurement results of the proposed structure demonstrate its sensitivity toward the available EM energy with nearly 100% absorption efficiency and very stable performance (greater than 75% absorption ratio) for incident angles from theta = 0 to theta = 70.
Furthermore, individuals carrying mobile devices into a measured area will affect the energy level for the respective frequencies that the devices operate at. A single detector can be placed within a defined area to provide crowd estimation within a specific radius (e.g., a room, an elevator, or a platform). Alternatively, multiple detectors can be tiled throughout a defined area to provide a crowd distribution.
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