Calibration of a chemometrical model from field hyperspectral close-range images: Taking into account leaf inclination and multiple reflection effects

The aim of the study was to test the potentiality of field close-range hyperspectral images to obtain nitrogen content of wheat leaves in field. Field measurements imply several potential disturbances of the recorded signal: illumination level, specular reflection, multiple reflections, etc. Chemo-metrical model calibration procedure has to take them into account. We tested the following methodology. First we calibrated a chemometrical model between nitrogen content and non-disturbed reflectance signal of flat isolated leaves. Thus we evaluated the quality of such a model. Then, we identified and qualified each phenomenon effects and proposed a solution to overcome each issue. Finally, we verified that all the disturbances could be taken into account while preserving satisfactory model prediction quality.