Smaller, Faster Lidar Could Map Seafloor from Aerial Drones

A lidar system light enough to fly on a drone and fast enough to process highly distorted signals in real time could enhance underwater mapping and security.

Firing a high-power green laser 10,000th of a second, a prototype built at the Georgia Tech Research Institute allows researchers there to study the best methods for producing accurate images of objects under several feet of water.

The system is suspended on a gantry over a laboratory pool, an arrangement that simulates flight over a water body.

Research engineers Eric Brown, left, and Ryan James examine the lightweight lidar prototype, which is gantry-mounted over a laboratory water tank. Courtesy of the Georgia Tech Research Institute.

Because real-world seawater will refract, scatter and absorb the lidar beam to varying degrees, the signal-conditioning and processing capabilities of the system must be sophisticated enough to extract reliable information from the noisy environment.

The researchers have devised a new approach called total propagated uncertainty to estimate the accuracy of sea-floor measurements in real time. To achieve the necessary processing speed, the team employed a mixed-mode computing environment composed of field programmable gate arrays (FPGAs), along with central-processing and graphics-processing units.

“In our laboratory tests, we’re computing about 37 million points per second — which is exceptionally fast for a lidar system and gives us a great deal of information about the sea floor in a very short period of time,” said principal research scientist Dr. Grady Tuell.

At nearly 600 pounds, today’s aerial lidar systems require costly, piloted aircraft to carry them. The research team’s long-term goal is to develop a system that weighs 30 pounds or less, which would allow it to fly on an unmanned aerial vehicle. Most of the necessary signal processing would be done on the aircraft, and only essential data would be transmitted to ground stations.

“We’ve provided a prototype that demonstrates the key technology, and we’ve completed a design for a mid-size design,” Tuell said. “In the future, we believe small bathymetric lidars will perform military tasks, and also civilian tasks such as county-level mapping, with increased convenience and at greatly reduced cost.”

For more information, visit gtri.gatech.edu.