Excessive deforestation adds carbon into the atmosphere, then some deforested areas rebound, and the growing trees act as carbon sinks, pulling carbon out of the atmosphere. Satellite images have long been able to see how much land area is covered by forest. Estimating the amount of carbon from conventional two-dimensional images is unreliable, he said, because they cannot measure tree heights, how densely the trees grow, or the thickness of the tree canopy. Using a new digital data analysis technique developed at Goddard, scientists from Goddard, the University of Maryland and other universities, and University of Maryland graduate students Birgit Peterson, Laura Rocchio and Jason Drake, were able to make estimates of tree canopy height, the amount of leaves and branches in a vertical column, and even the underlying topography of the land surface. The LVIS instrument, developed by Goddard engineer Bryan Blair, is a wide-swath, airborne laser altimeter or lidar, which stands for light detection and ranging.
Lidar works by sending pulses of laser energy to the Earth's surface.
The laser energy interacts with leaves and branches and reflects back to the instrument. What are uncovered are not only tree heights and the ground level below, but what's in between. The Costa Rica mission is a test for a laser instrument that will fly on the first of NASA's Earth System Science Pathfinder missions in May 2000. The mission is led by the University of Maryland, which is responsible for all elements of the program, from the spacecraft to the final data products. Dubayah, principal investigator on the VCL mission, said that researchers have used the new method to study coniferous forests in the Sierra Nevada of California and eastern deciduous forests of the mid-Atlantic region around the Chesapeake Bay.