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GCN : April 2013
It's faster than a speeding bul- let. It can measure buildings in a single pulse. It can scan the ocean floor and peer through forest canopies to measure un- dergrowth. It's LIDAR -- light detection and ranging. A standard LIDAR system emits a beam of light from a laser source and then captures the returned light in sensors as it bounces back from a reflect- ing object, measuring the dis- tance by calculating the time re- quired for the round trip. While LIDAR systems were used by the federal government as early as the 1960 --- primarily for atmo- spheric studies --- it wasn't until after 2000 that a combination of factors resulted in a boom of LIDAR data-gathering projects that are now bearing fruit at federal, state and local govern- ment levels. U.S. troops have used LIDAR to map the difficult terrain in Afghanistan and a Colorado State University scientist used it in creating the first forest height map to measure carbon cycles in ecosystems. "It's being used by just about everybody who uses a map," said John English, LIDAR data coordinator for Oregon's De- partment of Geology. "Every municipality and county is us- ing it. The Department of Land Management and the U.S. For- est Service use it for their forest inventory surveys." According to English, the agencies are increasingly turn- ing to LIDAR because the tech- nology has gotten both less expensive and more accurate, and, because surveys are gen- erally done from aircraft, vast amounts of territory can be cov- ered quickly. "It's been a huge timesaver," he said. "The esti- mate of savings is incalculable." Kirk Waters, a program man- ager at the National Oceanic and Atmospheric Administra- tion's Coastal Services Center, agrees. "LIDAR is a way to get fairly accurate elevations over a broad area at a reasonable price," he said. Waters pointed to a March 2012 report by the U.S. Geo- logical Survey that found that a national program of collecting LIDAR data would result in net benefits of between $116 mil- lion and $620 million a year. According to the study --- the National Enhanced Elevation Assessment --- the biggest sav- ings are to be realized in flood risk management, infrastruc- ture and construction manage- ment, natural resources conser- vation, agriculture and water supply management. Elevation data can tell city planners where to plan mitiga- tion for floods. It can tell farm- ers where to expect irrigation runoff and where to plant crops that require the most expensive fertilizers. Cities are using LI- DAR to build 3D maps. In all, "the study came up with 600 different uses," Wa- ters said. "There's just tons of applications." "It's at the beginning stages," said Steve Snow, a mapping and LIDAR specialist with geospatial tech company Esri. "Everybody is learning about the technol- ogy." Esri, in fact, just added the ability to import native LIDAR directly into its industry-stan- dard ArcGIS software. HOW IT WORKS In principle, the technology be- hind LIDAR is simple. By mea- suring the time it takes light to bounce off an object, and know- ing the speed of light (186,000 miles per second), one can de- tect the distance of the object. The challenge has been in devel- oping equipment that can fire rapid pulses of light --- in some cases up to 150,000 pulses per second --- and that can measure With improved technology and lower costs, light detection and ranging has brought fine-grained, 3D capability to "just about everybody who uses a map." HOW LIDAR IS RESHAPING MAPS, GEOSPATIAL DATA BY PATRICK MARSHALL 22 GCN APRIL 2013 • GCN.COM