Questão 34 - IME - 2ª Fase Dia 4 - IME 2025

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Drones Could Spot Crime Scenes from Afar

A system could aid forensic searches and crime-scene mapping by detecting reflections from human materials

BY RACHEL BERKOWITZ

1              Volunteers sometimes spend months trudging through remote terrain to search for lost hikers or crime victims.
         But a new tool could soon pinpoint forensic evidence from the sky instead. By identifying how traces of blood and
         other human signs reflect light when found on various natural surfaces, the scientists say searchers will be able
         to quickly scour large areas for clues about missing persons—dead or alive—using images acquired by drones.

5              Special drone-mounted sensors can record wavelength intensity for the entire electromagnetic spectrum
          (rather than just the red, green and blue of a typical camera) in each pixel of an image. Geologists routinely use
         this technology to pinpoint mineral deposits. Mark Krekeler, a mineralogist at Miami University in Ohio, and his
         colleagues realized that the same approach, supported by the right spectral data library, could potentially detect
         forensic evidence.

10              To build their tool, the researchers measured how human-related features, including blood, sweaty clothing
          and skin tones, reflect different wavelengths of light. Previous studies have examined such reflective “signatures”
          to identify blood, “but the signature depends on the surface itself and may change over time,” Krekeler says. He
          and his team analyzed thousands of samples, such as bloodstains on different rock types, recording how they
          changed as the blood dried.

15              The researchers customized software that mixes the known reflective signatures of various surfaces to
          reproduce a target of interest. For example, rock and clothing signatures can be combined to seek a hiker
          lost in the mountains, or a blood signature can be mixed with those of clothing and sand to search for a wounded
          person in a desert.

                The software estimates whether the target exists in any pixel in an image. It can distinguish between na
20      animal and a human in dense forest, search a cityscape for evidence of a specific person in a blue cotton dress,
          or determine whether soil is stained by blood or diesel fuel, Krekeler says. His team was slated to present its
          work at the Geological Society of America’s meeting of the North-Central Section in April.

              Wendy Calvin, a planetary scientist at the University of Nevada, Reno, who was not involved with the study,
          calls it “an interesting and novel use of spectral data—and the technique looks promising.” But she says it could
25     be challenging to use from afar because of how much of a substance would likely be needed to show up in a
          pixel.

              Within months, officials will be able to download and test the tool for themselves. Developing best-practice
          protocols for search teams could make such technology routine for investigations and forensics, Krekeler says.
          As drones and sensors become more widespread, he adds, they can transform investigations that are currently
30     costly, labor-intensive or even impossible.

Available at: <https://www.scientificamerican.com/article/drones-could-spot-crime-scenes-from-afar/> [on May 1st,2024].

According to the text, what challenge did researchers face in identifying blood using reflective signatures?