Airborne thermography of vines canopy : effect of the atmosphere and mixed pixel on observed canopy temperature.
Résumé
This paper explores the potential of airborne thermal infrared imagery to estimate the temperature of a vine canopy. Experiments were performed at several elevations (from 250 m to 1500 m). The effect of the atmosphere and the occurrence of mixed pixels need to be investigated to know how to correct the measured temperatures from these factors. Two models of corrections based on realistic assumptions were proposed and tested. The atmospheric correction was based on a simple approach which requires the measurement of ground references. It was shown to be effective, providing an estimation of the ground temperature with a RMSE of 0.9 °C. The correction of mixed pixels considers the temperature of the soil and the proportion of the soil and canopy within the pixel. Information on the proportion of canopy at the ground level could be derived from a multispectral image (i.e. NDVI). In the case of a discontinuous canopy like vine, the experiment highlights the significant incidence of mixed pixels on canopy temperature assessment. The correction improved significantly the estimation of the canopy temperature. However, the RMSE remained high (~1.6 °C) showing that our approach doesn't take into account the whole complexity of the phenomenon.
Domaines
Sciences de l'environnement
Origine : Fichiers produits par l'(les) auteur(s)
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