Given the current Covid-19 pandemic, thermal cameras are receiving increasingly more interest. It is a natural idea to utilize a thermal camera to detect elevated body temperatures. Right now, the Internet is full of information on the subject (including brand new companies), but it’s difficult to understand what is real, what is wishful thinking and what is exaggeration. At Eagle Eye Networks we have purchased a number of thermal cameras and have run a series of tests to determine what is practical with today’s technology. This document details some of the testing we have done and some of our conclusions. We do not claim that our testing is comprehensive or perfect, but we hope, that in sharing it, we can help.
This document focuses on the application of thermal cameras to read human body temperature. However, it is important to note, that before the Covid-19 pandemic, thermal cameras, at least as it relates to video surveillance, were primarily used for detecting perimeter breaches. This use case does not require the same level of precision that a thermal camera detecting an elevated body temperature requires. Therefore, typical general-purpose thermal cameras in the market have an accuracy of +/- 5 degrees Fahrenheit, which is not accurate enough to detect elevated body temperatures.
It’s also important to note that elevated temperature screening is not screening for coronavirus or for any other illness. In fact, some people who have a virus or illness may not have an elevated body temperature. Additionally, the majority of thermal cameras are not approved for medical use or approved by the FDA, but they may be well suited to provide an initial reading to allow appropriate personnel to perform follow up evaluation and potential diagnosis.
Executive summary
Thermal cameras can be used to detect elevated temperatures in humans under the right conditions. Creating those conditions can be challenging, but it’s not impossible or impractical. Our experience in testing has shown that the preferred solution includes cooperative subjects and limits measurement to a small number of people simultaneously. Given appropriate conditions we have tested cameras and found they consistently report temperatures within +/- 0.7 degrees Fahrenheit of measurements taken with a traditional thermometer.
System components
There are various systems in the market place; however, most cameras that are connected to a traditional surveillance system include these:
- Camera – Thermal and Visible Spectrum.
- Thermal Calibration Unit (blackbody).
- Recording System/ Video Management System.
- Local Display Device (optional).
Cameras
Some of the more advanced thermal cameras are effectively two cameras in a single housing, these are known by several different names – dual spectrum and bi-spectrum are the most common names. The image below (Figure 1) is a dual spectrum camera from Sunell that was designed to resemble a panda bear. This was originally deployed in Chinese schools where children would look at it as they entered.
Each camera produces a video stream, the visible spectrum camera works like most typical surveillance cameras. The thermal camera produces an image that is a visual representation of the different temperatures it has detected. These images can be either in grayscale or in color. Most cameras have several visual choices for how to represent the thermal data.
The images above (Figure 2) are from a dual spectrum thermal camera connected to the Eagle Eye Cloud VMS. This is a traditional video surveillance dual spectrum thermal camera, not a camera used to detect elevated body temperatures. There are a few things to note about the images. One is that the field of view is different. The visible camera can capture a wider field of view than the thermal camera. The visible camera has two vehicles in the field of view while the thermal camera only has one. The visible camera captures the street at the top of the image, while the thermal camera does not. The difference in camera field of view is quite common. Also, the thermal camera has a much lower resolution. The figures appear more ‘blocky.’ Thermal cameras today are generally much lower resolution than visible spectrum cameras.
Thermal calibration unit
A thermal calibration unit, sometimes referred to as a blackbody, is a device that maintains a specific temperature and does not reflect any energy from the surroundings. It is used as a constant point of reference for the thermal camera. Not all thermal cameras require a calibration unit, but many can make use of them if they are present. A calibration unit requires electrical power, but is not wired to the camera or the VMS/ recorder. It is manually set at a prescribed temperature, and the thermal cameras are configured based on that temperature. Thermal calibration units are typically used when more precise temperature readings are required such as in elevated temperature screening. Some suppliers include a thermal calibration unit with the sale of the camera, but most do not. Calibration units are generally not present for most cameras connected to a video surveillance system. Many security industry personnel are not familiar with thermal calibration units or their use.
Recording system/ video management system
The cameras are generally connected to a recorder. For this discussion we utilized the Eagle Eye Cloud VMS with its enhancements for support of elevated temperature screening. The cameras are connected to an Eagle Eye Bridge. As shown above (figure 2), The Eagle Eye VMS records both the visible spectrum camera as well as the thermal camera. Additionally, Eagle Eye VMS captures the temperature measurement data that the camera generates. This means that the temperature is associated with specific to me, so searches can be performed based on the temperature, time or person. Notifications can be generated if the temperature is outside of a specified range. In other words, if the temperature is too high, a notification can be made. The notifications can be delivered via various methods, but the most common is via email. Typical notifications will have an image of the person, the temperature detected, as well as name and location of the camera that detected the high temperature.
Local display device
An optional local display is sometimes used to provide immediate awareness of detected temperatures. This is essentially a display monitor connected to the recorder showing the real time feed of the visual and/ or thermal camera. This can be useful for awareness; however, it can be hard for a human operator to read every temperature reported in real time. It is more reliable to use a system that has alerts than to rely on a human reading a screen in real time. Many systems include a bell or an alarm if over temperature is detected.
Real World Situations
As different parts of the world reduce shelter in place guidelines many businesses and organizations look for solutions to provide environments where their employees, customers and visitors feel comfortable. There have been various news reports about companies using thermal cameras as a pre-screening tool to determine if individuals need further evaluation due to elevated body temperature. Additionally, some businesses are using humans and a hand-held thermometer to measure temperature.
Using a hand-held thermometer
Hand-held thermometers are generally available and fairly easy to use. Most families have one in their medicine cabinet. Using one seems like a good idea, and it will likely work for a small number of people. However, as the number of people entering a building increase, the number of people performing screening must increase as well. The level of consistency and accuracy decreases as the number of screener increases. In addition, with most hand-held thermometers the readings must be written down or transcribed into a computer system manually. It is difficult to develop a system and make this reliable. Furthermore, there is a risk to the screener, who needs to come close to the subjects being screened. We have had reports of screener being uncomfortable in such proximity to so many people, and therefore not properly using the hand-held unit, and thereby rendering the screening process completely unreliable.
Using an automated dual sensor thermal camera system
An automated system certainly introduces some challenges, but it solves a number of issues. An automated system needs to be properly installed and calibrated, but then human error is largely removed. It is best used as a pre-screening operation. As subjects move through the screening area their temperatures are read automatically, and depending on the deployment, the temperatures may be stored and notifications generated if the temperature exceeds a specific threshold. These subjects could then be routed to another location for further screening.
This approach allows for a greater number of subjects to be screened and it reduces the reliance on human screener.
It does require a second step to further measure subjects that are identified by the pre-screening, but the volume of subjects requiring secondary screening is a small fraction of the total number of subjects entering the building. The dual sensor solution is not perfect, the advantages and disadvantages, including cost, need to be weighed for each situation.
Eagle Eye VMS Integration and Features
The Eagle Eye Cloud VMS integrates with three specific aspects of the most thermal cameras. Eagle Eye Networks record the video stream, the thermal stream, and the temperature data for each subject. These are three independent data sources, that when combined can be powerful sources for reporting and alerting. The details of how this data is used and stored are described below.
Recording & retention
The Eagle Eye VMS records the video streams from the thermal cameras. This works with both single spectrum and dual spectrum cameras. These video streams are securely stored for a duration of 7 days up to five years, depending on the situation. Furthermore, parts of the video, or ‘clips,’ may be archived for a longer duration and easily shared with third parties.
Alerts & reports
An administrator can configure alert thresholds and distribution lists for people to notify if a temperature exceeds that threshold. In other words, if there is an individual with a body temperature of 100 degrees Fahrenheit, a notification could be sent to a site manager. This alert could be an email or a push notification to their cell phone or tablet.
Reporting is also available to show a count of the number of subjects screened, and how many were above and below the threshold. Additionally, authorized users can view the video of the readings that caused the alerts.
User access
Each user has his own unique ID and password to access the EE Cloud VMS. Eagle Eye Networks provides a robust, granular permission system. This allows specific cameras to be viewed only by specific users. This includes viewing video, making changes to settings, running reports and more. The system can be accessed with any modern web browser from a Windows or Apple computer or from dedicated iOS and Android mobile apps. Access can be from within the same building as the cameras, across town or even from a different country. Multiple users can access the same set of cameras and view the cameras at the same time, regardless of their location. In an elevated temperature screening application the data related to people’s health and temperature is private information. It is important that it be secured.
Simplified setup
The Eagle Eye VMS has been designed for easy set up including the network. The first part is the connection from the camera to the Eagle Eye Bridge. This is accomplished by either using a PoE switch or using an Eagle Eye Bridge with integrated PoE. Simply use an Ethernet cable to connect the camera to the switch, and then use another ethernet cable to connect the switch to the port labeled ‘CamLAN’ on the bridge. This will allow the Bridge to manage the camera network, as well as isolate the cameras from the internet, providing a layer of cybersecurity.
The second part of the network setup is to connect the Bridge to the Internet. This is done by connecting an ethernet cable from the ‘WAN’ port on the Bridge to your Internet connection (i.e., network router, WAN connection, cellular router etc). Once the physical connection is done, the configuration can be done from a laptop, mobile phone or tablet.
Not only can the initial configuration be performed easily, so can follow on maintenance.
Cyber security
The Eagle Eye VMS was built with a foundation in cyber security with multiple facets of protection. The two key concepts relevant to thermal camera deployments are the cyber camera lockdown and the fact that Eagle Eye Bridges do not require inbound ports and will only communicate with the Eagle Eye Cloud.
The cyber camera lockdown isolates cameras from the internet. This is important because it prevents anyone accessing the camera directly from the internet and it blocks any communication from the camera out to the internet. In the past, some cameras have had malicious code installed. The cyber camera lockdown prevents this code from being able to communicate with any outside systems.
Additionally, the method the Bridge uses for communication with the cloud prevents external systems or malicious users from communicating with the Bridge, and by extension the cameras connected to the Bridge. The Bridge initiates the connection with the Eagle Eye Cloud. This connection is at secure tunnel that is authenticated via certificates. These methods and techniques ensure that only authorized users can view video and prevent compromise of the system.
Eagle Eye Elevated Temperature Testing Example #1
We have spent approximately 4 weeks testing thermal cameras for elevated temperature screening. This is not an exhaustive study at this point. However, we have been testing in some real-world situations as well as lab comparisons. We have built up a reasonable body of knowledge. The testing we have done has been with individuals and pairs of subjects. We have not tested large groups of people. A number of tests and comparisons have been run.
We will detail one such test below:
Setup #1
Our setup is indoors, close to the entrance of our office in Austin Texas. The cameras we tested recommend 10- 13 feet of distance from the measurement point to the camera. Figure 4 below shows the equipment in place.
The thermal cameras were calibrated with the calibration unit. They are connected to the Eagle Eye VMS using an Eagle Eye Bridge. There is also a local display monitor which shows the live view of the cameras including temperature readings. This setup is on a rolling cart, which is not ideal for a long-term installation, however, it worked well for our tests.
Test methodology
As subjects entered the building, their temperatures were automatically captured by multiple thermal cameras. The subject’s temperature would then be taken using a forehead contact thermometer. We used a QQcute MODEL FT100A.This thermometer is rated with an accuracy of +/- 0.4 degrees Fahrenheit.
Testing – Round One
We tested seven subjects three times each and recorded the results. Fortunately for our subjects nobody had an elevated temperature. Unfortunately for our testing this meant that we had to determine a way to simulate an elevated temperature. We tried several different methods including a hot towel and a hair dryer, but we ultimately settled on a ceramic. Ceramic retains heat reasonably well. The ceramic disk was submersed in hot water of a specified temperature (typically100 to 105 degrees F). The ceramic disk would then be held to the forehead to simulate a warm body temperature. This is not a true and accurate simulation of an elevated body temperature, however, it does test how the system behaves when it detects an elevated temperature.
Test Equipment – Round One
The following table outlines the different equipment used in the test.
Test Results – Round One
We found the thermal camera was on average within +/- 0.7 degrees Fahrenheit of the forehead thermometer.
These tests were not conducted in a laboratory, they were conducted in the unpredictable environment of our office. So, while they’re not scientific, they represent real world usage patterns.
Recently the FDA released updated guidance for telethermographic systems. In this guidance their recommendation is to have a device that has an accuracy of +/- 0.9 degrees Fahrenheit.
As can be seen by Table 2, the thermal camera’s results are always less than the hand held thermometer. The difference ranges from -0.4 to -1.0 degrees Fahrenheit. One way to look at the data is to use the average difference of -0.7 degrees as an offset from the thermal camera to the hand held. Once that off set is applied then all of the thermal camera readings are within +/- 0.3 degrees of the off set. Using this methodology, one could simply adjust the target temperature they are looking for by -0.7 degrees and set the alerting threshold based on that number. In other words – if someone is looking for subjects with a temperature of 100 degrees, they could set the alert threshold to 99.3 degrees.
Testing – Round Two
As of April 24, 2020 testing is still ongoing. This document will be updated as soon as results are available.
Thermal Cameras in The Market
There are many camera manufacturers that provide thermal cameras. This section is not meant to be an exhaustive guide, but rather a description of the more common manufacturers in the physical security market. Other cameras will be added as they become available.
Conclusion
Our testing has shown that dual spectrum thermal cameras detect human body temperature to an accuracy of .7 degrees Fahrenheit in a real-world scenario. This is within the FDA guidelines of .9 degrees margin of error. We realize that this is not a scientific proof and certainly not enough to be used exclusively for the safety of your employees, guests, visitors, friends or family. However, we do believe it to be a useful tool for initial screenings, in the proper environment. Like most tools it can be used as intended or it can be abused, it all depends on who is controlling it.
We believe that many businesses, organizations and possibly government entities will require some sort of temperature verification as shelter in place requirements are lifted and people return to work and recreation. Thermal cameras, properly configured, with appropriate alerting and reporting capabilities may be one way to achieve these goals.
Eagle Eye is committed to continue to investigate, innovate and deliver to help now, and in the future.
