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article imageNew laser scanner finds unmarked graves

By Tim Sandle     Aug 19, 2018 in Science
The laser based technology LiDAR might be more commonly associated with the development of autonomous cars, but it has another application of interest to pathologists: finding unmarked graves.
Scientists have been developing a new approach to detect unmarked gravesites in a way to speed up crime detection. The new development comes from geospatial researchers working at the U.S. Department of Energy’s Oak Ridge National Laboratory. The researchers have been collaborating with forensic scientists from the University of Tennessee.
The new application makes use of advanced laser scanning together with 3D modeling techniques based on as LiDAR (“light imaging, detection, and ranging”). LiDAR is a type of surveying method that assesses distance to a target thorough the illumination of the target using pulsed laser light. Sensors then measure the reflected pulses.
By calculating differences in laser return times and wavelengths, these parameters can be used to construct digital 3-D representations of a target. Today LiDAR is being used for a number of terrestrial, airborne, and mobile applications. The technology is perhaps best known as a control and navigation system for many types of autonomous cars.
In a different application of the technology, the combination of the new methods allows researchers to track tell-tale signs of recently buried human remains. It is hoped that this new development will complement current procedures used in forensic casework to try and located recently buried bodies.
Among the current methods is ground-penetrated radar. This method is good for detecting anomalies on surfaces, such as recently moved earth, but it is limited in terms of the size of an area that can be assessed.
A remote sensor like LiDAR could improve upon this and be operated from a greater distance, which enables investigators to assess a larger area in their search for a body.
A tripod-mounted terrestrial LiDAR sensor can scan a vast area. In tests, the researchers assessed an area four times over a 21-month period. They succeeded in collecting millions of data points and used this to build a digital picture of subtle changes to a ground’s surface.
Variations of interest would include where elevation change is observable at disturbed surfaces, and bears unique qualities and elevation change bearing the same qualities is not observed at undisturbed surfaces. In this context, soil disturbance results in elevation gain, followed by elevation loss, then stasis. This study observed surface elevation activity for up to four months post-burial.
According to researcher Katie Corcoran: “Unmarked graves are difficult to locate once the ground surface no longer shows visible evidence of disturbance, which poses significant challenges in finding missing persons.”
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