A team of researchers from the University of León (UL; León, Spain; www.unileon.es) and the University of Santiago de Compostela (USC; Santiago de Compostela; www.usc.es) were able to carry out an inventory of vineyards in the El Bierzo designation of origin area by using a teledetection system.
Vineyard areas were previously checked by tracing the borders of each plot by hand on photographs. "The new method is based on computerized analysis of the crops using digital images taken by a Landsat satellite," according to José Ramón Rodríguez-Pérez, co-author of the study and an agronomist engineer at the UL.
The study, which has recently been published in the Spanish Journal of Agricultural Research, includes analysis of two photographs of the El Bierzo area taken three months apart, in order to compare the data obtained each time. After in situ validation in order to determine the margin of error, there was an 88% success rate for those areas planted to vines.
This system can distinguish between up to 18 different types of surfaces in the images, including roads and areas planted to crops, pasture, irrigated land, or forested areas, and can extract the area covered by vineyards from these.
The electromagnetic spectrum information in the photographic images obtained from the satellite can be separated into seven different bands. Once the image has been sent to Earth, the researchers apply a series of algorithms, which analyze the photograph pixel by pixel, identifying the 18 types of surfaces. To pick out the vineyards, the software needs a series of test areas to be defined. "We knew what kind of crop was in which area, and we created a pattern with the spectral characteristics of each," explains the study's author.
The program also differentiates between three types of vineyard -- recently-planted ones, those with a ground density of less than 35%, and those with a density in excess of 35%. In this case, the degree of precision is only 30%, but Rodríguez-Pérez points out that new tools are being designed using high-resolution spatial photography.
The researchers hope these will provide more exact results; "as always they must be checked in the field -- the teledetection system is not a final procedure in itself, but it does help make it easier to carry out an inventory of vineyard areas," says Rodríguez-Pérez.
For more information: José Ramón Rodríguez-Pérez, Carlos José Álvarez López, D. Miranda, M.F. Álvarez, "Vineyard estimation using medium spatial resolution satellite imagery," Spanish Journal of Agricultural Research, 6 (3), pp. 441-452, 2008.
