Scientists from the Aerospace Information Research Institute (AIR), Chinese Academy of Sciences (CAS), have proposed a new algorithm called AGAR, which makes it possible to detect tree heights only using 10-cm stereoscopic imagery, according to a study published in Remote Sensing of Environment on May 10. Current knowledge on the limitation of stereoscopic imagery is obtained based on analysis of satellite images with spatial resolutions of 15-m to 2-m. Changes of ground surface elevations are in the same scale with that of forest stand heights under this spatial resolution. It is indeed difficult to separate them from this viewpoint. Scientists found that 10-cm stereoscopic imagery enabled the separation of the mixture at the scale of trees instead of forest stands by making use of image segmentations and allometric equations. Validation results using UAV stereoscopic imagery under different terrain conditions showed the AGAR algorithm could effectively separate terrains from forest heights, capable of providing more reasonable predictions of tree heights with minimal influence from terrains.
