Martin Ecarnot

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.

A spectral correction method for multi-scattering effects in close range hyperspectral imagery of vegetation scenes: application to nitrogen content assessment in wheat

A method able to overcome multiple scattering effects in close range hyperspectral imagery of vegetation scenes is presented. It has been developed using canopy and light propagation simulation tools and evaluated on real crop plants in the context of nitrogen content assessment.