Satellite images of vineyards in France, Chile, and Brazil are used to study spectral differences between the vine varieties Cabernet Sauvignon, Merlot, Pinot Noir, and Chardonnay, to verify if features of a given variety are conserved at vineyards in completely different terroirs. Data are eight images from ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) orbital sensor, for years 2000, 2001, 2002, 2004, and 2006. Additional information is from maps of properties, field surveys and GPS measurements. In France, data is from the Champagne region (Pinot Noir and Chardonnay), and Bordeaux (Cabernet Sauvignon and Merlot); images of Chile are of Aconcagua Valley (Cabernet Sauvignon, Merlot); in Brazil, data for all varieties are from the Serra do Sudeste region. All spectra are expressed in reflectance values, across the nine spectral bands of VNIR (Visible and Near Infrared) and SWIR (Shot Wave Infrared), which are ASTER detection subsystems. Corrections for atmospheric absorption are applied. It is assumed that vine leaves are the dominant source of radiance. Spectra and NDVI for each variety, for every terroir, are generated. Results are: a) spectra of Cabernet Sauvignon and Merlot are similar to each other, over all regions; b) Pinot Noir and Chardonnay also have similar, characteristic spectra; c) spectra from later stages in the phenological cycle tend to have smaller reflectances; d) for each variety, the characteristic spectra has a stable configuration, even when measured in different terroirs and at different epochs; e) NDVI values confirm the two-by-two grouping of varieties. It is concluded that, despite large differences in terroir, spectral features of each one of the studied varieties are conserved.
Authors: Gisele CEMIN, Jorge Ricardo DUCATI
Centro Estadual de Pesquisas em Sensoriamento Remoto e Meteorologia
Universidade Federal do Rio Grande do Sul
Av. Bento Gonçalves 9500 – CEP 91501-970
Porto Alegre, Brazil
Email: ducati@if.ufrgs.br
Keywords: remote sensing, spectral signatures, satellite images, terroirs