DURHAM, N.H. (AP) — University of New Hampshire researchers are looking at data from laser imaging of forests with the goal of helping foresters and landowners track tree inventories to save them from the time-consuming practice of heading into the woods with tape measures.

Mark Ducey of the New Hampshire Agricultural Experiment Station has been investigating how aerial and ground light detection and ranging – better known as LiDAR – can be used to provide more accurate and detailed information about forests. The technology maps three-dimensional land surface elevations.

“You can spot things like old cellar holes, stone walls and wagon roads from when an area used to be a field,” Ducey said. “Just being able to spot old cellar holes, which are hazards, is helpful.”

With aerial LiDAR, a plane flying over the land directs a rapidly pulsing laser toward the ground. The laser sweeps back and forth, collecting data to complete coverage.

A detector measures how long it takes for each beam of light to travel to the ground and reflect back to the plane.

Travel time is converted to distance based on the speed of light, resulting in numerous closely spaced ground elevation data points.