This graphic image of the La Mosquitia rainforest in Honduras was derived from lidar observations. (University of Houston)
For decades, explorers have been searching for a lost Mayan city called Ciudad Blanca — the White City — deep in the nearly impenetrable, virgin jungle of Honduras’ La Mosquitia region. A new book called “Jungleland” recounts a monthlong trek to find the legendary place, a trip plagued with despair, bugs, illness and danger. In the end, it is unclear whether the expedition found the spot or not.
But the ruins of Ciudad Blanca may at last have been found, not by a weathered adventurer wielding a machete and maps, but by a low-flying Cessna 337 equipped with a red laser that maps surfaces beneath trees.
Called lidar, for light detection and ranging, the three-dimensional laser-mapping technology is fast opening up the world to discovery and analysis like no other. It is providing valuable insight for archaeologists, climatologists — and military planners.
Lidar came into its own as an ISR tool during the war in Afghanistan. The National Geospatial-Intelligence Agency used it to map the entire country, outlining contours within meters of accuracy for road building and infrastructure development.
But lidar is also opening up the rest of the world in new ways. On the eastern U.S. seaboard, geologists are using it to map shorelines and analyze coral reefs to track climate change. And the team that provided the lasers to find the Honduran structures may soon be flying to Guatemala for another archaeological search, and next year, to map Antarctica.
As the apparent discovery of the White City shows, much of the world, even in regions close to the U.S., is barely mapped.
“There is a lot to be learned, a lot,” said Ramesh Shrestha, who directs the National Center for Airborne Laser Mapping (NCALM) at the University of Houston. “We don’t know anything, especially with thick jungle canopy.”
Lidar systems can be built with different sensors, depending on the kind of data is desired. A green laser can help map underwater topography. Other lasers, many still in development, could help determine specific surface characteristics of the object being mapped. Adding thermal sensors can provide a wider, richer range of information to be collected.
Increasingly, all of this information will be transmitted from the airborne collection platform in real time.
“There is potential capability to be over the dense forest and understand what lies underneath, whether it be drugs, enemy or agriculture,” Shrestha said.
Near-infrared laser is unable to directly penetrate vegetation, but the points can slip through tiny gaps in foliage wherever there is space for a beam of light. That’s enough, in the jungle, for the technology to do its work.
Picture it like this: In old navigation, sailors would lower a weight into water to measure the distance to the bottom. Samuel Clemons famously adopted his moniker ‘Mark Twain’ from the call marking of two fathoms of depth. In lidar, there’s no string attached to a weight, but it’s a similar process. A laser beam pulses at the speed of light several million times a minute, bouncing back with information about the surface below to create a three-dimensional image. And unlike previous jungle-penetrating radar technologies, Shrestha said, lidar can, in the best of circumstances, produce readings whose accuracy is measured in tens of centimeters.
SEARCH FOR CIUDAD BLANCA
Shrestha said Steve Elkins, an explorer and filmmaker who began his search for Ciudad Blanca more than 20 years ago, heard of NCALM after reading of the facility’s discovery of other historical ruins in Belize in 2009. Elkins pushed to deploy the technology in the hunt for the mysterious lost city. With the approval and collaboration of the Honduran government, the overflights were scheduled over a period of two months in early 2012.
Four 20-square-kilometer sites were targeted for overflights by the center’s Cessna 337 twin-engine aircraft. Flying slowly at 600 meters above the surface, it fired up to 100,000 laser points per second, Shrestha said. That translates to up to 35 measurements per square meter, or about three laser points per square foot.
The data collected showed a picture of the jungle canopy and the ground beneath it in a cloud of data points. Using software that strips the data of the canopy from the three-dimensional image, a contoured image of the surface below emerged. In two of the sites, they got lucky.
In a Honduran hotel, one evening after a flight, the scientists looked at the preliminary analysis and found something they knew had to be man-made.
“What we found is geometric shapes, rectangular and pyramidal structures that were unlikely to be made by nature,” he said. “That is when we got excited.”
Explorers will still have to trek to the buggy muck of the jungle to see if the structures they found are really the lost city, but at least this time, they’ll know where they are going. An expedition is planned for sometime this year, he said.
MAPS OF THE FUTURE
The excitement around lidar isn’t contained to archaeological discoveries. In the next five to 10 years, the intensity of lasers is expected to increase by orders of magnitude, boosting portability and driving costs down.
Ten years ago, an airborne lidar system could fire 3,000 points per second. Now, there are systems nearing 800,000 points per second.
Companies such as Optech, Reigl and Leica offer a range of devices. Large manufacturers like Boeing have also become involved, producing a backpack-size device that, if anything, heralds the future of portability of these devices.
A system used in Afghanistan called ALIRT, or Airborne Ladar Imaging Research Testbed, was designed by the Massachusetts Institute of Technology’s Lincoln Laboratory. (Ladar stands for laser detection and ranging.) From October 2010 through 2011, the ALIRT plane flew more than 150 flights in Afghanistan, rendering three-dimensional images at altitudes up to 9,000 meters, according to the university.
ALIRT was also deployed following the 2010 earthquake in Haiti to track large-scale movements of people and communities in the days afterward and help plan the reconstruction, according to the military and the university.
The U.S. Geological Survey, which, like many government agencies, contracts much of its laser surveying to private companies, is using its lidar research to map the floor of the Barnegat Bay in hurricane-devastated New Jersey and provide data for new nautical charts. USGS is also surveying the coastline to predict sea-level rise and minute changes in topography to guide reconstruction in flood-prone areas, said John Brock, a scientist coordinating lidar research for the USGS Coastal and Marine Geology Program.
“Now I think the advances are to map more under forests and more mapping through water, and we are heavily involved with that,” Brock said. “To understand coastal hazards, storms and tsunamis and other major things in the next 50 to 100 years that are going to happen with sea level rise.”
In a market analysis released by IBISWorld researchers in December, growth in the $116 million domestic lidar industry was expected to increase steadily at a rate of nearly 5 percent through 2017. It is buoyed by civilian uses ranging from the topographical mapping of planets to urban planning to implementation in adaptive cruise-control systems in vehicles.
The Defense Advanced Research Projects Agency has also pushed forward a rapid deployment system. The project had the capability to map half of Afghanistan in 90 days, testified Regina Dugan, the director, in 2011.
Shrestha, the University of Houston professor, sees a smaller, cheaper future for lidar combined with other sensors that are together mounted on UAVs.
He points to efforts by Boeing to mount lidar aboard the high-altitude Phantom Eye surveillance drone project. And he highlights how lidar on smaller drones could provide real-time intelligence on obscured enemies or weapons.
“Within 10 years, that will come along,” he said. “You can imagine how that will affect, generally, the mapping of the surface of the earth.” å
This story appears in the March 2013 issue of C4ISR Journal