3D Dense Reconstruction of Plant or Tree Canopy Based on Stereo Vision

Three dimensional (3D) reconstruction of the plant or tree canopy is an important step in order to measure canopy geometry, such as, height, width, volume, and leaf cover area. In this research, binocular stereo vision was used to recover the 3D information of the canopy. A revised camera calibration method was provided to calibrate the cameras in world coordinate system. Only two images were used to realize a dense reconstruction. These two images were firstly rectified to make sure the corresponding feature points in the left and right images were on the same horizontal line. An efficient large scale stereo matching (ELAS) algorithm was used to find the disparity map. The plant or tree canopy was finally reconstructed based on these calibrated camera matrices and the disparity map through a triangulation method. A plant (croton) with big leaves, a citrus branch, and a small citrus tree with small leaves were used to test this two-view dense reconstruction. It was easy to measure the geometry of the big leaf. Two big leaves from croton plant were used to measure the width and length of the leaves. The measurement from the reconstruction and manual measurement showed that this reconstruction was metric reconstruction. Another four reconstructions were completed based on a side view of the croton plant, a top view of the croton plant, a top view of a branch from a mature citrus tree, and a side view of the citrus tree. All these gave good 3D visualization of the objects