ESTIMATION OF THE HEIGHT AND ANGLES OF ORIENTATION OF THE UPPER LEAVES IN THE MAIZE CANOPY USING STEREOVISION

3D models of vegetation have been constructed to allow various simulat ions, such as the interception of incoming radiation, radiative transf er, reflectance simulation in remote sensing, study of plant function, and interspecies competition. The construction of such 3-D models is based upon simple geometric assumptions and several production rules ( eg, growing, branching). It poses 2 problems: the acquisition of a lar ge amount of data on leaf heights and orientation angles in the field; and the validation of the model and assessment of its suitability on the scale of the field. This paper presents a method of 3D acquisition and reconstruction based upon stereovision, ie upon the acquisition o f data using 2 synchronized CCD or photographic cameras. We first show that Toscani's method of camera calibration can be used under real co nditions in the field. We then apply the method to a tall maize canopy (2.50 m high) because this canopy allows easy control measurements to be made in the field. Results on the estimation of position and orien tation of the leaves are presented. This method allows the estimation of the X, Y and Z coordinates of characteristic points of laminae and stems. The ability of the method to provide inclination angles of the leaves was evaluated to be rather good. Only the leaves belonging to t he 4 upper layers were reconstructed because of the difficulties due t o hidden areas. This problem is discussed and we show how auxilliary i nformation on crop structure may be complementary to data obtained fro m stereovision.