In Urban Search and Rescue (USAR) operations, and in particular structural collapse incidents, search cameras are one of the important technical search tools can help the USAR team to narrow down the search area and locate trapped victims inside debris speedy and safely. This article will introduce the international requirement and the application of the search cameras.
Search methods in USAR
According to the International Search and Rescue Advisory Group (INSARAG) Guidelines, the USAR teams are required to fulfil five key components, i.e. Management, Search, Rescue, Medic and Logistic, and mainly focus on large-scale structural collapse incidents. In these incidents, lifesaving activities usually occur in confined spaces. As is well known, the search methods comprise surface/physical search, technical search, and canine search. In order to have sufficient ability to conduct comprehensive searching for further rescue operations, the USAR teams are required to have the capability for canine and/or technical search, depending on the capacity level.
There are many detectors for the same purpose. Some are designed to detect the electron kinetic energy of the human heartbeat through vibrations and sound waves. However, a search camera is a common tool for technical search. There are three types of search cameras based on the wavelength, including visual, infrared and ultraviolet. In the electromagnetic spectrum, optical and infrared signals are both commonly used for life detection.
In actual incidents, search teams can locate the victims in debris by an optical life detector with a flexible and long probe to obtain images through holes or gaps in the surface of debris. However, if there are no gaps, the team needs to make one using equipment to improve the time and success rate of the search for the victims. Since it is an optical technique, the quality of image could be affected by polluted water on scenes where it is flooded.
With the rapid development of technology, the new search cameras in the market have more functions. For example, new optical life detectors can detect sounds or vibrations made by trapped victims with a 360-degree view. It helps to locate the victims rapidly in earthquakes, mines, landslides and other disasters. In addition, infrared search techniques are introduced, which can show a clear picture even in total darkness. The infrared search technique can be divided into active detection and passive detection. The active infrared life detection technology uses the infrared searchlight to generate infrared radiation to detect the target, processes the corresponding reflected signal and finally converts the electrical signal into the vision signal that can be recognized by the human eye, so as to detect the existence of the living body. This technology can accurately detect people and animals and the distance to them, but it is highly reliant on imaging technology. But the weather, such as fog and sand and ground vibration will cause the system to give false positives.
In contrast, passive infrared life detection technology does not emit any infrared radiation itself but passively receives infrared radiation from the detected target (temperature above 0), which is then converted into a thermal image, such as a thermal imager. The advantages of this technology are lower cost and good concealment, but it cannot penetrate obstacles such as walls.
With the in-depth research of scholars in the world, infrared technology is widely used in search and rescue operations. With the emergence of a variety of image fusion theory and algorithms, nowadays image texture data and details can be combined with thermal radiation. The targets are highlighted and analysed, improving the efficiency and accuracy of search operations.
Application methods and advantages of optical life detectors
At present, the optical life detector is one of the search tools for USAR operations. As mentioned, the search team can locate victims by the probe which carries video devices and microphones, so that the rescuers can communicate with the victims inside the debris. The signal can be transmitted by cable and optical fibre.
Before using an optical life detector, the team will assess the condition. The base lens can also be turned by the user operating the device in order to capture even the most difficult-to-reach corners and spaces. If the potential victim is trapped in the surface area, the search team can select a short rod, while the long rod can be used for a victim trapped in a deeper area. In case the search team is required to search inside a vertical shaft, an extension line is needed. As mentioned, the optical life detector relies primarily on holes or gaps in debris, therefore, the team needs to drill several holes to speed up the operations.
The rescue team can assess the condition and select the most suitable rescue plan to save victims, based on the information collected by the search team. The main advantages of using technical search are:
1. Can directly observe the trapped victims and the conditions inside the debris through image and audio.
2. More reliable compared with other search methods.
3. Can use an optical life detector as a safety monitoring tool.
4. Easy and simple to operate.
The below table can show the difference of various technical search equipment:
Searching is the one the critical phase in USAR operations because rescuers rely on the information collected by the search team to conduct rescue lives in disaster scenes. In order to ensure the accuracy and sufficiency of the above information, reliable search equipment is important. In recent years, new technology has vastly improved the way the search is carried out, both in terms of accuracy and working conditions.