Lidar technology took a giant leap forward with the advent of Geiger-mode lidar, which features a more complex sensor system and lower laser-energy requirement. Initially used exclusively for military purposes, it has now come onto the commercial market, enabling aerial surveys to be conducted with unprecedented flight altitude and area yield, dramatically lowering the cost of geospatial data acquisition.

Traditional linear-mode lidar systems repeatedly fire a single high-powered laser pulse. This can be problematic because vegetation or other surface features can break the beam into multiple return signals or block it entirely.

Geiger-mode lidar, in contrast, uses a photodiode array to flood an area with infrared light. Each diode in the array is sensitive enough to detect a single photon reflected from the illuminated area. The array is mounted on a scanner that rotates at an angle to create a cone-shaped field of view. This results in a circular ground field of view rather than a line as with linear-mode lidar. As the scanner rotates, the photodiode array flashes up to 50,000 times every second and takes 4,096 measurements per flash, equating to 205 million samples per second. As a result, each square meter of terrain can be sampled thousands of times in a single over-flight.

Dense illumination of the surface allows Geiger-mode lidar to see through obscurants like trees and other vegetation. Moreover, Geiger-mode lidar can be flown at altitudes of up to 45,000 feet, creating a larger ground swath for the sensor, allowing faster data collection.

Geiger-mode lidar’s speed and affordability make periodic monitoring practical. Utilities, for example, can now use it more often to monitor power-line corridors for vegetation encroachment, a major cause of line failures and power outages costing economies billions of dollars annually. The technology is also helping to design smarter cities, improve transportation systems, maintain utility infrastructure, and plan wind and solar farms more efficiently.

Harris Corporation first developed the Geiger-mode Avalanche Photodiode in conjunction with Lincoln Laboratories at MIT. After more than 15 years of refining this technology for the Department of Defense, Harris introduced the first commercially available Geiger-mode lidar sensor in 2015, shortly after it was declassified.

The technology now finds use in private-public partnership with the U.S. Geological Survey (USGS) to advance the national 3D Elevation Program (3DEP), which is collecting elevation data across the United States as part of the broader National Geospatial Program, which aims to provide a foundation of digital geospatial data representing the topography, natural landscape, and manmade environment of the United States. The program supports a wide range of applications, including projects related to energy infrastructure construction and safety. 3DEP is expected to generate $13 billion in new economic benefits yearly through applications spanning the economy.

 

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Posted by Paul Nash