Underneath the thick, virgin rainforest cover in the Mosquitia  region of Honduras, archaeologists have discovered ruins they think may  be the lost city of Ciudad Blanca. Legends say the "White City" is full  of gold, which is why conquistador Hernando Cortes was among the first  Ciudad Blanca seekers in the 1500s.     
But the method the modern researchers used was a little different  from previous explorers' techniques. The modern-day researchers flew  over the area in a small plane and shot billions of laser pulses at the  ground, creating a 3-D digital map of the topology underneath the trees.  
This is one of the first times this technique, called light detection  and ranging (LiDAR), has been used to map ancient ruins. Beyond  archaeology, LiDAR researchers at the National Science Foundation are  looking to develop the technology for mapping disasters using drones, for military spying and for tracking erosion under rivers and shallow parts of the ocean.  
LiDAR for archaeology Before LiDAR improved enough for their work, archaeologists  discovered ruins the old-fashioned way — by hacking through forests  using machetes. LiDAR is faster and cheaper.
It's been gaining ground since 2009, when a U.S. archaeology team  working on Maya ruins first used the technology to peer beneath 80  square miles (207 square kilometers) of forest canopy in Belize. After  four days of laser scanning, team members discovered buildings and  agricultural fields they hadn't found in 25 years of study. The team was  supported by the then-new National Science Foundation organization for  LiDAR science, the National Center for Airborne Laser Mapping. [
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Airborne LiDAR works by sending more than 100,000 short laser pulses  to the ground every second while a plane flies over the area of  interest. The laser light hits the ground, then returns to the aircraft.  The time it takes for the light to make the back-and-forth trip tells  researchers the altitude of points on the ground.  
The technology is able to detect height differences of less than 4  inches (10 centimeters) and maps to GPS coordinates within 4 to 8 inches  (10 to 20 centimeters). "It's within a step, in many cases," said Bill  Carter, University of Houston engineer who develops LiDAR systems for  the National Science Foundation.
The Belize archaeology work and the new Honduras findings both used  the National Center for Airborne Laser Mapping's LiDAR system. There was  one major difference between the two projects, however. At the Belize  site, researchers thought it was likely there would be new ruins there.  They used the LiDAR to scan regions surrounding structures they had  already uncovered. On the other hand, in the new study in Honduras,  researchers were running on just a hunch — and plenty of private  funding.  
LiDAR in Honduras Cinematographer Steven Elkins has been fascinated with the  Ciudad Blanca stories for more than a decade. He previously analyzed  satellite imagery of the Mosquitia forest, looking for signs of the  city. As LiDAR improved, he gathered private investors to pay for the  National Science Foundation's laser mapping center to analyze three  areas he thought were especially promising. Elkins had originally  approached the Honduran government with his idea, but government  officials said they knew the forest well and there wasn't anything  there, Carter said.
Over several days, National Science Foundation engineers flew over  about 60 square miles (160 square kilometers) of forest for Elkins in  their dual-engine Cessna planes. At the end of every day, they sent the  data to Carter, who was working out of West Virginia. Carter found the  first signs of what appeared to be human-made structures within five  minutes of analyzing the data, he said. [
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"I'm the only person right now on the planet that knows that there's  these ruins," Carter recalled thinking when he saw what he said were  straight lines and right angles that don't normally appear in nature.  "My wife walked in and looked over my shoulder and she was the second  person to know."  
Carter sent his analysis back to the archaeologists in Honduras, who  agreed the structures were man-made. Now, Elkins, along with a team of  Honduran scientists, will visit the structures in person and determine  what they are and how old they are. The LiDAR coordinates will help them  pinpoint exactly where to look in the thick jungle.  
LiDAR for biology, disasters and the military Carter said he found his involvement in discovering the  Honduras ruins exciting, but the National Science Foundation's LiDAR  center is looking to do much more with the technology.  
So far, center researchers have used LiDAR to map to the ground to assess flooding risk and to 
find new fault lines in  California. They've pinged Floridian citrus groves with lasers to check  on the trees' health. Healthy tree leaves reflect a different quality  of light back to LiDAR sensors than do sick trees, Carter explained.
The science agency also recently developed a laser that uses green  light, which is able to map features underneath shallow water.  Biologists want to use this technology to investigate fish spawning  grounds, Carter said, while land managers may use a water-LiDAR to keep  an eye on erosion.  
In the future, the center hopes to develop smaller, lighter, less  expensive LiDAR that is able to ride in unmanned robotic aircraft. The  drones could spy for the military, go on a tough Arctic mapping  expedition or assess conditions after disasters, such as earthquakes or  hurricanes.  
"As we look in the future, we see the ability to use these types of  systems to map the entire Earth," Carter told InnovationNewsDaily.  "Certainly all the land areas and shallow coasts."
Msnbc.com