How it Works

  • UWB Technology
  • How to Setup
    A Survey
  • How to Read the
    Survey Results

Ultra Wideband Technology

Ultra wideband (UWB) signals have been used for decades in geophysical applications. When UWB signals are used in geophysical instruments, the sensor is moved in order to detect and map underground objects. When used in GSSI’s LifeLocator®, the sensor is stationary to detect motion and breathing characteristics.

UWB signals are generally defined as electromagnetic transmitters whose bandwidth is at least 25% of the nominal center frequency. UWB operates in the time domain; almost all other transmitters operate in the frequency domain.

Geophysical instruments are moved across a surface and transmit very short bursts of electromagnetic energy into the ground. Reflections from buried objects are received at another antenna. This technology can detect targets such as plastic pipes and voids underground, and inside walls and floors. Any change in dielectric property of materials will cause a reflection. Reflections from targets will arrive at different times depending on their distance from the antenna (and will also vary depending on the type of material through which the signal passes).


For GSSI’s LifeLocator®, the transmitted and reflected signals are primarily passing through debris and air. The sensor is stationary and detects moving objects. As with geophysical analysis, the approximate distance of the object causing the reflected signal can be determined by the particular time delay in the signal return. The monitored area may approximate a cone with a beam width of 120 degrees and a range as large as 30 feet. There may be concrete walls or other structures and obstacles in the radiation path.

  • Total average power is transmitted is ~1% of a cell phone
  • Working in the time domain, distance to the motion can be measured

The reason for using a UWB signal instead of a single frequency transmitter is improved motion resolution, distance measurement and obstacle penetration. Lower frequencies within the transmitted pulse carry further, especially when looking through walls and floors; however, resolution is coarser with lower frequencies. Since the resolution is a function the wavelength of the transmitted signal, higher frequencies will provide finer resolution. In the simplest terms, the wide spectrum of the transmitted signal accommodates most motion and obstacle types. In essence, a maximum number of frequencies are transmitted (both low and high frequencies) with the notion that some frequency will be reflected and sent back to the receiver.

Setup the Survey

Deploying the LifeLocator® is simple and easy. Here is a basic how-to method for a successful survey:

  1. Determine the appropriate grid/survey area.
  2. Place the sensor on the ground/debris material.
  3. The Control Unit, if operating in Locate View, will display red circles or black squares if the unit has detected signs of life. The red circles indicate breathing, while the black squares indicate motion.
  4. To determine how far the victim is located from the sensor, there is a distance indicator on the right side of the screen. Use this to determine how and where the victim is located.
  5. If nothing has been detected within 3 minutes, move on to the next grid selection and continue with the search.

Optimize Survey Results

  • Tip 1: Placement Interval spacing is not always easy to determine. Typically, we suggest that one would search every four meters in a grid pattern for adequate coverage. Searchers may need to reduce the grid pattern interval under wet or muddy conditions. Placement-angle and rubble stability may make an idealized search pattern nearly impossible.
  • Tip 2: It is important to remember that radar cannot see through metal. Placing the sensor on a metal backed concrete slab, a chain-link fence or a metal screen will not work. However, seeing through concrete with rebar mesh usually works fine, since the spacing is typically more than six to ten centimeters.
  • Tip 3: Consider outside interferences, remember to clear the area around the sensor before gauging results of the survey. Also, be aware of how one’s communication devices may interfere with data results.

Unlike conventional search and rescue tools, the LifeLocator® system uses ultra wideband (UWB) technology to improve the odds of recovering living victims of structural collapses. Using this technology, teams can detect the movements and breathing of victims caught in debris. Shown below are graphic representations of what breathing (red circles) and motion (black squares) detection look like on the tablet screen in simple Run Mode.

LifeLocator TRx Detection Modes

Locate View

The LifeLocator TRx has several modes to view the data. Locate view allows the users to identify life detection through a simplified display. Motion detection is illustrated by black squares and breathing detection is shown as red circles. The stronger the detection confidence, the larger the shapes appear.

The graph also displays the approximate distance to the target, note the representation of the sensor and the distance of the moving and breathing target beneath. Additionally, the lung icon indicates the target’s breathing rate.

Expanded View

Expanded view allows the user to view and interpret the raw data. An additional feature includes detection icons to indicate breathing (red circles) and motion (black squares) in the same view.

Yellow highlights indicate areas of interest. The white line represents the estimated signal floor. Users can toggle between Locate view and Expanded view with one button on the control unit.



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