By Elizabeth Preston
One strike against the human species is that we’ve filled the Earth’s oceans and beaches with garbage. A point in our favor, though: We’ve figured out how to use 3-D laser scanners to automatically measure and analyze that trash, which could help assess the problem and prioritize efforts to clean it up. We might even mount those laser scanners on robots.
The world needs a better method for tracking shoreline refuse, says the coastal researcher Zhijun Dai at East China Normal University in Shanghai. A beach littered with plastic bags and cigarette butts might ruin vacation Instagrams, but it’s even worse for a seabird, fish, or endangered turtle that eats garbage or gets tangled in it. Various countries and international groups have systems in place to monitor debris on their beaches. The National Oceanic and Atmospheric Administration (NOAA), for example, relies on volunteers to track trash on North American shores, especially along the Pacific coastline, by mapping out transects along beaches and tallying up any garbage they find that’s more than an inch across. OSPAR, a group of European countries that works together to protect the Atlantic, also has a long-standing protocol for monitoring beach litter. But this kind of manual counting is tedious—surveyors have to work one glass bottle, bendy straw, or Styrofoam wedge at a time—and subject to human error. In Japan, researchers are using webcams to look for plastic pieces on some beaches. But this method is limited by light and weather conditions, and gives only a two-dimensional view.
Dai and his colleagues decided to demonstrate that trash counting can be done by laser—specifically, by light detection and ranging (LIDAR). This method bounces laser pulses off objects and uses the echoes to map an environment. It’s often used to survey landforms, forests, or archaeological sites. The dense, three-dimensional rendering that results is called a “point cloud.”
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