Automatic presence detection solution allows you to always maintain a safe social distance

Few could have predicted that social distancing would become so pervasive in our daily lives in such a short period of time. In the early days of the global pandemic in 2020, people felt great anxiety and stress due to social distancing. Some people used to be less concerned about the size of the physical distance radius, but now they have to maintain a strong sense of safe distance. What does one meter of social distance really look like? What should we do when we and the people around us have different estimates of one meter of social distance? Social distancing has proven to be problematic even in outdoor spaces. Social distancing has become more complicated for customers who have to continue shopping for food and daily necessities for their families. Stores were asked to implement new distancing policies and shopping processes overnight to help customers strengthen social distancing behaviors in narrow and often crowded aisles inside stores.

Social distancing is likely to be a mainstay of the retail shopping experience for the foreseeable future, so stores will need to implement better, more automated, and customer-reliable social distancing measures. This article will explore technology solutions that can facilitate social distancing in retail stores. We will discuss a variety of options, from occupancy density indicators to absolute social distance measurements, so that readers can consider options with varying complexity and cost.

Space occupancy density indication

Monitoring the number of customers in a specific area of ​​a retail store is a simple but effective retail social distancing method. Most food stores and other stores with aisle layouts have implemented one-way aisle diversion methods to reduce the flow of people from multiple directions and increase awareness of one-meter social distance for customers entering the aisles from the entrance, but this practice has little effect, and many customers do not actually notice or comply with the one-way aisle regulations, which greatly reduces its effectiveness.

Some very simple technical solutions can at least provide an indication when a customer has entered the aisle by mistake or when the aisle has reached its limit. Simple physical sensing technology, similar to that used in home security monitoring systems (usually passive infrared, time-of-flight, microwave, reflective optical or ultrasonic sensors, either alone or in combination), can be used at both ends of the aisle to determine whether a customer is entering or exiting the aisle. However, this requires not only knowing that a customer is present, but also which direction they are heading. The solution is to place a series of sensors at the "entrance" and "exit" of the aisle and monitor the order in which the sensors are triggered. If the outermost sensor triggers but the innermost sensor does not, someone may have started to enter the aisle but then exited. If the outermost sensor triggers and then the innermost sensor triggers, someone has entered the aisle; if the innermost sensor triggers before the outermost sensor, someone has exited. This trigger information can be processed centrally to determine the direction of customer travel and spatial occupancy density, and an alert signal can be issued to indicate that a shopper has entered the wrong direction or that the aisle cannot accommodate more customers.

Similar to the highway ramp lights that keep vehicles entering the highway at a safe distance, this approach could be used to develop a shopping aisle “traffic light.” Each aisle could be equipped with a light that would keep customers at a safe distance from each other by estimating how long it would take them to walk one meter along the aisle (including shopping activities).

In stores without aisles, this type of solution has some limitations. Also, once customers are in the aisles, enforcing social distancing will not be effective. However, it may be a cost-effective way to enforce aisle direction and flow restrictions.

Absolute social distance measurement

There are indeed many technologies that can be used to monitor the exact location of each shopper in a retail space. In fact, these solutions are not necessarily much more complex or costly than the customer density indicator methods mentioned above. Each solution should consider not only the relative cost of the core technology, but also how many sensor nodes need to be deployed. The complexity of the system is also related to the number of nodes and the data collection, processing and transmission methods.

Optical Sensors

Optical sensors are a common way to track the exact location of people in a given space. In practice, most stores already have surveillance cameras installed around the store, so this may be a relatively easy solution to deploy, depending on the coverage of the existing camera infrastructure. If the current infrastructure coverage is not high, small optical sensor nodes can be installed around the store, and the number of nodes will mainly depend on the field of view and any visual obstructions between the nodes and the monitored space. The image can be processed at the edge sensor node, and the sensor will issue an alarm in real time if there is an abnormal occupancy of the space in the area. In order to detect occupancy anomalies between two different nodes, for example, if two people are too close to each other, but each is captured by a separate and adjacent optical sensor, the sensor data needs to be processed centrally. Both visual sensors and thermal imaging sensors can be used for this application scenario.

Radar/LiDAR

Similar to optical sensors, radar and lidar sensors can be used to accurately find out the location of each person in a given space. Both systems have longer detection ranges than other optical solutions, so the number of sensor nodes required can be reduced in some applications. However, in stores, especially those with aisles, obstacles are likely to cause problems. In this regard, radar systems require higher customization, considering the physical structure of each specific deployed system, which will limit the modularity or scalability of radar and complicate installation.

Pressure Sensor

Pressure sensing flooring is another viable method for social distancing monitoring in retail stores. Floors equipped with pressure sensors (MEMS, strain gauges) can detect the presence or presence of heavy objects (people, shopping carts), and therefore can also provide accurate location information based on the known location of the sensor itself. Several companies abroad have proposed pressure sensing floor solutions for retail social distancing to track and analyze shopper behavior. However, this method requires the deployment of a large amount of infrastructure and may require more equipment in the context of social distance monitoring.

Microphone Array

Ultrasonic microphones have proven to be a very effective presence detection solution because they are so sensitive that they can detect even breathing sounds and can distinguish sounds even when there is a lot of background noise. This method can also be used for social isolation purposes, but microphone arrays have limitations when distinguishing more than two people. This method may require a lot of signal conditioning and intelligent processing.

RFID electronic tag positioning or partitioning

In environments where shopping tools such as shopping carts or baskets may be used, such as food stores or supermarkets, RFID electronic tag technology can be used to determine the location of shopping tools. Each shopping cart or shopping basket can be equipped with an RFID electronic tag, and the location of the shopping cart or shopping basket can be determined by readers around the store. RFID positioning uses triangulation to determine the location of the tag based on the relative signal strength of the tags read by multiple readers. In RFID zoning positioning, the RFID reader is set to measure only shopping tools in a specific area, so the target tag must be located in that area. Both methods can effectively determine social distance in a retail environment; however, they only reflect the location of the shopping cart or shopping basket, not necessarily the location of the customer using the shopping tool. Obviously, this does not work if someone is not using such a shopping tool.

Wi-Fi/Bluetooth

The industry is currently evaluating the use of mobile Wi-Fi and Bluetooth location technology for social distancing and infection tracking. Some stores track customers in and out of stores based on phones searching for Wi-Fi signals. Bluetooth-based mobile phone applications allow users to customize the radius of their "personal space" and alert users when another Bluetooth device intrudes within the radius. These technologies have wide applicability not only in retail environments but anywhere social distancing is a concern. Wi-Fi will be limited in outdoor situations, but mobile data networks can be used instead.

This approach requires that the individual has an Internet-connected device (usually a mobile phone) and that connectivity is enabled, so it is limited by user usage factors. In addition, some users may have privacy concerns about being tracked in this way and worry about the possibility of data being leaked from the device. However, this approach is certainly better than having no protocol at all, and for retailers, this system is quick to deploy with limited infrastructure investment.

Conclusion

Innovative solutions are essential to the ongoing adoption of new norms for daily activities. There are a variety of technologies that can help achieve social distancing measures, which is particularly important for retail activities where even at-risk people cannot avoid them. From basic functions such as indicating the occupancy of a space to precise measurements of social distance limits, the type of sensing technology selected will determine the functionality of the solution. In addition, by combining some of the technologies described in this article, a reasonable solution can be customized to meet any application requirements. Many of these technologies can be developed in a very short period of time, and as social distancing parameters change, the technology solutions will continue to improve and better suit various applications and use cases.