Spectral features of vineyards in south Brazil from ASTER imaging

Abstract

Analysis of spectral features of vineyards was performed by using satellite images and field radiometry. The possibility of identification of grape variety was investigated. Multispectral satellite images from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor were used to study two regions in the Rio Grande do Sul State, Brazil. These regions are 500 km apart and have significant differences in relief, soil and climate, and in the culture associated with vine-tending and wine-making. Applying the concept of ‘terroir’ as a geographical unit whose specific descriptors transmit an identity to the products coming from it, both regions were considered to be distinct terroirs, with respect to viticulture. For one terroir, with plots of up to 10 ha and vines in rows, spectral information from nine ASTER bands is given for 13 Vitis vinifera varieties. For the second terroir, which has smaller plots and vines supported by continuous trelliswork, radiometric field measurements provided spectral information in addition to ASTER data. The results are that the vineyards are positively identified in the ASTER images; the satellite image data are compatible with field radiometric measurements, in the sense that the grape varieties observed with both methods show reflectances with similar behaviour; the spectra of a given grape variety, taken from three different plots, are mutually consistent; parcels of white and red grape varieties can be separated into classified orbital images; and the spectral information is influenced by the terroir. It is concluded that ASTER images are a valuable tool for vineyard observation and monitoring, applied to area measurements and grape variety identification, leading to multiple applications, including precision viticulture.