Earlier this month, scientists working on NASA’s ABoVE field campaign performed ground surveys of a birch forest in the Tanana Valley of interior Alaska. The ground surveys complement data collected in 2014 using the so-called G-LiHT airborne imager, which produces views that can’t be achieved using satellite imagery alone.
In a newly released 3D image, varying colors correspond to different tree heights. Shades of yellow represent the tops of the tallest trees (measuring up 82 feet or 25 meters), while the dark-purple shade represents the ground, according to NASA’s Earth Observatory. This technique makes it easy for scientists to see that most of the trees in this forest are of uniform height, the agency said.
G-LiHT, short for Goddard’s lidar, Hyperspectral and Thermal imager, is known as an imaging spectrometer, and is capable of collecting three different types of data to study the composition of the forest. Lidar, responsible for making the image 3D, stands for light detection and ranging, and is a remote-sensing method (similar to radar, which employs radio waves) that uses pulsed laser light to measure ranges.
Hyperspectral cameras can collect image data far outside the spectral range of the human eye. The electromagnetic spectrum spans low frequency waves (like microwaves) to gamma rays, which are high frequency. The visible light spectrum is a small segment that falls on the shorter end of the spectrum, and contains the wavelengths that humans can see.