GRU Airport, the administrator of São Paulo International Airport, announced last Tuesday (16) that it will use thermal cameras with black body calibrator on site. The aim is to identify passengers with elevated temperature (above 37.8º), which may indicate the presence of COVID-19.
The equipment was developed by Dahua Technology, a multinational electronic security company. According to its developer, its technology allows for greater precision in indicating people's body temperature, with a margin of 0.3°C. The company's equipment is already being used in airports in Spain, Turkey, Chile, Argentina, and Colombia, as well as in the Salvador subway system since June 1st. Furthermore, other public spaces in Brazil already have thermal cameras.
However, according to Dahua Technology itself, the distinguishing feature of the cameras to be used at the São Paulo airport is the constant, real-time calibration source for the camera, known as a black body. Operating continuously every day of the week, the cameras are installed at the boarding gate of Terminal 2. Through a monitor, GRU Airport agents will monitor the entire operation. If a passenger is identified with a temperature higher than 37.8°C, they will be directed to the airport's medical post to receive care and instructions.
Artificial intelligence
According to the multinational company, its cameras use a special calibrator operating with artificial intelligence, whose algorithms analyze the temperature proportional to the amount of infrared rays emitted by a person. Thus, it is possible to measure the temperature of up to five thousand passengers in just 30 minutes. Using a conventional thermometer, the analysis of the travelers would take 5 hours.
Measuring body temperature before boarding using a thermal camera is one of the measures that GRU Airport has been offering its passengers to combat the spread of the new coronavirus. The administrator states that several other recommendations from the National Health Surveillance Agency (ANVISA) are being followed by the concessionaire to combat and prevent the disease at São Paulo International Airport.
How does Black Body work to ensure accuracy?
When it comes to cameras capable of accurately measuring human body temperature, much has been said about the "margin of error" of 0.5°C plus or minus. But how can such precision be guaranteed over a long period of use without calibrating these cameras? As Dahuan itself explains on its website: this is not possible.
Thermal cameras, also known technically as infrared cameras, have a special sensor capable of converting the infrared radiation emitted by objects into an image visible to the human eye. Some of these cameras have algorithms capable of calculating the temperature proportional to the amount of infrared rays emitted by an object, person, or animal. After all, every object, person, or animal emits a certain level of infrared radiation, which we feel as heat. A hot object emits a greater amount of infrared rays than a cold object, for example.
Among manufacturers of thermal or thermographic solutions for measuring body temperature, some guarantee a temperature measurement accuracy of ±0.5°C using only a thermal camera. In controlled environments with constant temperature and humidity, this accuracy can be achieved, but when installing this equipment in building entrances, industrial gates, store entrances, shopping malls, and airports, where there are different incidences of sunlight and temperatures that change throughout the day, this accuracy will certainly not be maintained for long. The explanation is simple: with each temperature reading taken by the thermal camera, the error declared by the manufacturer accumulates, causing the temperature reference of that camera to change. With the reference changed, that same declared error is now applied to a new reference – that is, the final reading error becomes increasingly larger, potentially reaching ±1°C or even ±2°C over time.
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