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Near Real-Time Polarimetric C-Band SAR Observations of Vineyards: RADARSAT-2 watching the Italian Frascati wine area

Alessandro Burini(1), Giovanni Schiavon(2) and Domenico Solimini(2)

(1) Geo-K, Via del Politecnico 1, 00133, ROME, Italy
(2) Tor Vergata University, Via del Politecnico 1, 00133, ROME, Italy



The wine industry tends to enter a renewal phase, with a particular attention devoted to monitoring the end-to-end production process, from farming practices to cellar operations. Presently, vinification and refinement have started exploiting advanced technologies, while vine cultivation are more often left to the tradition, with overall results still heavily dependent on human factors and natural events. Indeed, the state of vineyards is monitored by inspections carried out by agronomists, who sample the fields at a necessarily limited spatial and temporal rate and at an overall cost that can be fairly high. Some wine producing countries, such as the U.S.A. (especially in California), South Africa and Australia, have introduced optical remote sensing to support and integrate the information acquisition on the vineyards, e.g., [1], [2], given the potential of the Earth Observation technology in providing information crucial to ameliorate wine production at relatively reduced costs. We add that satellite observations can also play a general role in agricultural landscape management, for instance when planning new vineyards, or when the urban expansion conflicts with vineyard conservation, affects cultivation and can result in degradation of wine quality or even of its safeness. On their side, radar images have been used mainly for vineyard mapping [3]. More recently, the sensitivity of backscattering to cultivation practices has been investigated, e.g. [4], [5], also in the attempt of identifying the contribution of grapes to the backscattering. To this end, an airborne experiment supported and organized by ESA within the BACCHUS-DOC project, was carried out in the fall 2005 [4], when L-band polarimetric and C-band dual-pol images were acquired over Frascati by the DLR E-SAR. The experiment outlined a relation between backscattering and biophysical vine parameters, but the poor time sampling (only two flights) and the peculiar climatic conditions did not allow to demonstrate a sensitivity of backscattering to grapes. It is worth to point out that the problem of measuring the grape parameters by radar is made difficult by the interfering scattering contributions from the stable woody structure of the vines, from the concrete poles and metallic wires supporting the runners, and from the soil and weed which add to the scattering from leaves and grapes. This contribution reports on monitoring vineyards in the Frascati, Italy, D.O.C. (Protected Designation of Origin - PDO) area by the new polarimetric C-band RADARSAT-2 during the grape ripening and harvest period, from August to October 2008.

RADARSAT-2 Dataset and Analisys of Vineyard Images

Within the Science and Operational Applications Research (SOAR) for RADARSAT-2 Program Project 1488, the Earth Observation Laboratory of Tor Vergata University, Rome, Italy, is now being provided with at least two fully polarimetric images per month and benefits from their prompt delivery (from few hours to 3 days). A total of 10 polarimetric acquisitions is scheduled between August and December 2008, with a closer time sampling during the ripening and harvest period in September and October. Images acquired on seven dates have been received up to now. All data have been calibrated, co-registered, geocoded and integrated into a G.I.S.. The experiment is being carried out on a test site selected in the Frascati D.O.C. area, located within an ancient volcanic complex South Est of Rome. The observed area has an overall surface of about 10 km2 and is characterized by sparse urban land cover mixed to agricultural fields. The slopes are generally gentle with several flat areas. Nine different vineyards have been selected, both with rows (oriented North - South and East - West) and with the spatially homogeneous tent structure. In addition, three forest stands, three grass parcel and four plots of arable land have been chosen in the neighborhoods of the vineyards. These regions of interest have been selected taking into account their slope, to reduce the effects of the different viewing and incidence angles and to achieve a satisfactory co-registration. A suitably stable estimate of the backscattering is achieved by averaging over at least 3 hectares. Thanks to the fully polarimetric dataset, different polarization basis are under consideration. For the time being, time series of the difference (in dB) between the linear cross-polar backscattering coefficient sigma_hv and the linear co-polar sigma_hh averaged over the parcel, have been plotted for each field. This backscattering ratio shows time variations up to 3 dB in the case of vineyards. The behavior in now under investigation to possibly understand the involved effects, also with the support of the observed ground truth. Maps of the degree of interferometric and polarimetric coherence are also being generated, as interferometric image pairs become availble, and the space-time variation of coherence is being studied in relation to the conditions of the observed vineyards.


[1] A. Hall, D.W. Lamb, B. Holzapfel, and J. Louis, “Optical remote sensing applications in viticulture: A review”, Australian J. Grape Wine Res., vol. 8, pp. 36–47, 2002.

[2] L.F. Johnson, D.E. Roczen, S.K. Youkhana, R.R. Nemani, and D.F. Bosch, Mapping vineyard leaf area with multispectral satellite imagery, Computers Electron. in Agriculture, vol. 38, pp. 33–44, 2003.

[3] J.L. Bugden, G. Salinas de Salmuni, and P.J. Howarth, “Vineyard identification in the Tulum Valley, Argentina, using RADARSAT imagery”, Proc. 4th Int. Airborne Remote Sensing Conf. 21st Canadian Symp. Remote Sensing, Ottawa, Ontario, June 1999, Vol. II, pp. 375–382.

[4] A. Burini, F. Del Frate, A. Minchella, G. Schiavon, D. Solimini, R. Bianchi, L. Fusco, and R. Horn, “Multi-temporal high resolution polarimetric L-band SAR observation of a wine-producing landscape”, Proc. 2006 Int. Geoscience and Remote Sensing Symp. IGARSS’06, Denver, CO, U.S.A., 2006.

[5] G. Schiavon, A. Burini, D. Solimini, “Sensitivity of multi-temporal high resolution polarimetric C- and L-band SAR to grapes in vineyards”, Proc. 2007 Int. Geoscience and Remote Sensing Symp. IGARSS’07, Barcelona, Spain, 2007.

[6] A. Burini, G. Schiavon, D. Solimini, “Fusion of high-resolution polarimetric SAR data and multi-spectral optical data for precision viticulture”, Proc. 2008 Int. Geoscience and Remote Sensing Symp. IGARSS08, Boston, MA, U.S.A., 2008.



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