Remote Sensing of Shaded Area in Vineyards
Airborne multispectral image data were compared with intercepted photosynthetic photon flux (PPF) in commercial winegrape (Vitis vinifera) vineyards of Napa Valley, Calif. An empirically based calibration was applied to transform raw image pixel values to surface reflectance. Reflectance data from the red and near-infrared spectral regions were combined into a normalized difference vegetation index. Strong linear response was observed between the vegetation index and PPF interception ranging from 0.15 to 0.50. Study results suggest the possibility of using optical remote sensing to monitor and map vineyard shaded area, thus providing spatially explicit input to water budget models that invoke evapotranspiration crop coefficient based calculations.