As the pulses bounce back to a receiver in the plane they will provide the raw data for a detailed three-dimensional image of the county.
The technology is called light detection and ranging; officials use the acronym LiDAR. The resulting map will have a multitude of uses from helping to control flooding to applications in agriculture and archaeology, said Sheena Beaverton, program manager of the Illinois State Geological Survey.
A practical application of its value was offered to the four dozen officials attending the meeting at the La Salle County Emergency Management Agency building in Ottawa by Anthony Heddlesten, an emergency management specialist with the U.S. Army Corps of Engineers.
Heddlesten said officials used a similar technology to determine low spots in the Illinois River levee in Tazewell County before the 2013 flood. The identified areas were “almost spot on” to where water would have have come up over the levee, he said.
“If we had not had the ability to do that then there would have been like 16,000 acres and 2,000 homes under water,” Heddlesten said. “Plus, we saved them a ton of work. They didn’t have to sandbag 16 miles, they only had to sandbag 10 places for 300 feet.”
There is nothing new about the program. The laser mapping of Illinois has been underway for several years, the pace depending on funding available from a combination of federal, state and sometimes county sources.
Ninety of the state’s 102 counties already have been mapped, and La Salle County will be the last county in the northern third of Illinois to be mapped.
FEMA has held off preparing new regional flood maps until the La Salle County data is available, she said.
“It’s a huge deal for county and for the surrounding counties,” said Ottawa Building Official Mike Sutfin.
Beyond flood predictions, there are numerous other uses, Beaverton told The Times.
For instance, in two counties large hog farm lagoons were planned over areas where laser mapping determined there were fractures in the bedrock of the area aquifers.
Also, she said, “in Illinois there has been a lot of subsurface mining. If the mine is old enough you can see its perimeter” on a laser map.
Other uses include the location and analysis of forested sinkholes and even archeological sites.
“If you have Indian mounds, they show up on LiDAR,” she said.