This essay, by Anja Zhang, 17, from Jerome High School in Dublin, Dublin, Ohiohe is one of the eight best winners of the Learning Network the third annual STEM writing competitionfor which we obtained 3,564 entries.
You can find the works of all our winning students here.
Right from science fiction blockbusters, light particles allow self-driving cars to discover surrounding objects, scientists to map the ocean floor, and even archaeologists to discover historical monuments. Light detection and range, or lidar, seem to use light molecules to “see” the environment around them.
So how is a lidar able to detect objects? Through laser pulses, light photons are emitted, interacting with various surfaces they encounter. Imagine billiard balls - the blow of a billiard cue sends the balls into flight, hitting the sides of the table or bouncing off each other until they fall into the corner pockets. Similar to billiards, some of the light particles bounce off the surface and return to the pocket of the lidar instrument.
By transmitting energy in “waveform”, lidar technology collects data on the time and angle at which light photons enter the instrument. Lidar compiles photons that arrive at a similar time and direction into energy jumps; larger spikes indicate that the light was reflected from an object or earth. Using these spikes and the k-, i- and z-coordinate information given by individual photons, the lidar can display a miniature surface. By merging these surfaces into a patchwork, the lidar can generate detailed 3-D views of the area, even representing tree leaves or cracks in the sidewalk.
Different technologies can also use unique types of light, depending on the purpose. For example, one of the two categories of lidar, bathymetry, uses the green light. This green light can penetrate water, making it useful for drawing underwater surfaces. Another category of lidar, topographic, uses infrared light: the classification of light at the lower end of the electromagnetic energy spectrum compared to green light. A topographic lidar is commonly used to map land characteristics and is used in smaller sensors.
Currently, smaller lidar sensors are used to detect speeding or to detect the road environment in self-driving cars. However, more powerful lidar technology has been implemented for a larger task: visual representation of entire land areas. In October 2021, Science News reported that lasers helped with the archeological discovery of the underground square and pyramids in Guatemala.
David Stewart, director of the Center for Mesoamerica at the University of Texas at Austin, explained that “there was no visible stone fence”, so “it was thought to be a natural hill”. Covered with earth and vegetation, the structures were camouflaged from the everyday eye. However, due to lidar maps collected by helicopters, archaeologists have harmonized the appearance of the “hill” with the appearance of a similar structure: La Ciudadela, a square located near Mexico City. This discovery led experts to discover hidden structures.
Beyond their archaeological implications, lidar charts provide a multitude of exciting opportunities. Scientists can use technology to characterize vegetation in different ecosystems or to plan efforts in the event of landslides or tsunamis. Regardless of its application, the lidar certainly makes the “easy” work of science fiction laser fantasies transforming the aspirations for 3-D mapping into reality.
Papers cited
Bauer, Bruce. “Lidar reveals a possible plan for many of the ceremonial sites of Olmec and Maya.” Scientific News, October 27, 2021.
Quain, John R. “What Self-Driving Cars See.” New York Times, May 25, 2017.
Rodrigues, Meghie. “Lasers uncover a structure inspired by the ancient Mexican pyramids in the Mayan ruins.” Scientific News, October 22, 2021.
Wasser, Leah A. “Lidar Basics - Light Detection and Range - Remote Detection.” Neon, October 7, 2020.
“What is Lidar and what is it used for?” American Institute of Geosciences, November 2, 2020.