Hovering over the calm waters of the lake, a strange device silently surveys every nook and cranny of the unseen depths. With laser beams dancing across the bottom, it paints an intricate drawing of data points revealing the lake’s mysteries.
From the deepest depths to the sunny beaches, LiDAR’s watchful eye holds the key to unlocking a world beyond what the naked eye can perceive. A thrilling adventure awaits those who dare to decipher the language of light.
In recent years, a technology called LiDAR, which stands for Light Detection and Ranging, has been making waves in various industries, from autonomous vehicles to video games. LiDAR is a remote sensing method that uses laser light to measure distances and create detailed three-dimensional maps of the surrounding environment. The U.S. Army Corps of Engineers has been using this cutting-edge technology to revolutionize the way we see and interact with the world and how we map our surroundings.
“LiDAR is an extension of data collection, dissemination, visualization, and analytics,” said Bryon Haney, U.S. Army Corps of Engineers’ Southwestern Division Geospatial Program Manager. “Accuracy and precision are everything, especially if you're going to drape LiDAR imagery over a photo and take a two-dimensional image and make it a three-dimensional surface. This is especially important when tracking sediment buildup and bathymetry in our reservoirs.”
Bathymetry is the study of underwater depths of ocean, lake, or river floors. In other words, bathymetry is the underwater equivalent to topography. NASA notes that early attempts to map the underwater world relied on shipborne methods like sounding lines made of lengths of rope and cable. But this could only measure a single point at a specific moment in time. Sonar allowed greater ease of measurement of vast bodies of water. Now LiDAR is painting a more accurate picture.
“We use photogrammetry [the art and science of extracting 3D information from photographs] and LiDAR to map our lakes,” said Bryson Webber, Fort Worth District Geospatial Services Section Chief.
According to the U.S. Geological Survey, LiDAR can be used to collect accurate data sets of lake-bed elevations. The lake-bed elevations and associated geographical position data can be merged with land-surface elevations. The Fort Worth District uses LiDAR to measure where water and land come together. The turbidity of lakes, or cloudiness of the water, fed by a river makes deep measurements with LiDAR difficult.
LiDAR also allows USACE to create detailed maps of dams and levees without disturbing the ground. By scanning the area from above and within, LiDAR can reveal any hidden faults, such as fissures or below water slides, that are invisible to the naked eye. This non-invasive approach has the potential to revolutionize dam maintenance as LiDAR can see what humans cannot. The data points collected from dams displays the depth of the water, the types of land surrounding it, and other critical design elements.
“One of the things LiDAR has allowed us to do is actually get precise measurements inside interior spaces as well as check for any potential erosion along a levee,” said Webber. “Before we either would have had to do manual measurements, or we could take videos and photos, but we wouldn't be able to get size measurements across the whole breadth of the conduit.”
Because of the lack of off-the-shelf electronics to do specific jobs, the Fort Worth District GSS has designed and built a rover to take measurements in locations which would be dangerous to send a person at a fraction of the cost of hiring a contractor to do the same work. They are also designing a remote-controlled boat for measuring above and below the water’s surface.
“The idea is to make a safer entry to evaluate [underwater] conduits and I have experience with building automated robotic equipment from previous work,” said Webber. “I've built unmanned aircraft systems in the past and that same technology works on the rover. So, after seeing the dam bot (a remote-controlled vehicle built on an ATV frame), I figured I could build something similar for a fraction of the cost.”
Beyond USACE, LiDAR is being used by significant state and federal partners such as the Forest Service, to accurately measure tree heights, canopy density, and biomass that surround our lakes. This data helps in assessing the health of forests, identifying areas at risk of wildfires, and planning sustainable logging practices.
According to Jeff Atkins, a research biologist with the Forest Service, forest managers and researchers within the Forest Service have been at the forefront of applying LiDAR to National Forests and beyond since the technology became broadly available in the late 1990s.
“The Forest Service is also using LiDAR for terrain and geomorphological applications creating digital elevation products,” said Atkins. “Work with three-dimensional LiDAR has included a heavy focus on fire and fuel load characterization, or measuring the amount of material on the forest floor and how flammable it is. The ability to map and monitor fuel loads in forests is crucial given the increase in wildfires over the last few years and decades driven by climate change, land use, development, and human encroachment and direct human interference.”
While LiDAR technology has already made significant advancements, its full capabilities are yet to be seen. Either used by itself or with other imaging systems, LiDAR is painting a clearer picture of our surroundings.
“LiDAR is enhancing and expanding what we do,” said Webber. “There’s no real way to detect minute changes or movement or current conditions without LiDAR.”