@TechReport{QueganYana:1987:DeChBa,
               author = "Quegan, S. and Yanasse, Corina da Costa Freitas",
                title = "Detection of changes in the backscatter from agricultural plants 
                         using agriSAR 86 data",
          institution = "ISPRA",
                 year = "1987",
                 type = "RPQ",
              address = "S{\~a}o Jos{\'e} dos Campos",
             keywords = "AgriSAR, dataset.",
             abstract = "The AgriSAR 86 dataset, incorporating meteorological, crop, 
                         ground-truth, corner reflector and image data for the Feltweell, 
                         UK, test-site is assessed for its ability to provide information 
                         on the spatial and temporal variation of backscatter from growing 
                         crops. The image data is shown to contain several sources of 
                         radiometric distortion which affect any attempt at image 
                         calibration. Of these, the simplest to correct is that caused by 
                         range interpolation in the amplitude data. All interpolated pixels 
                         should be discarded from the amplitude data supplied by CNES. 
                         Measurements made without first performing this correction are 
                         related to the correct values by an expression involving both 
                         additive and multiplicative terms. Correction from slant range to 
                         ground range is comparatively straightforward. Effects due to 
                         variations in antenna pattern, in the range and azimuth direction, 
                         require assumptions about the angular variation of the backscatter 
                         of crops and statistical homogeneity of ground cover before they 
                         can be removed. The properties of system noise appear complicated 
                         and are not yet properly characterized, but interfere with 
                         corrections for the antenna pattern. Correlation properties of the 
                         data appear to vary little between images, and hence the standard 
                         errors associated with sample statistics are comparable between 
                         images. Offsets in the two channels of the complex data also 
                         interfere adversely with antenna pattern corrections. The size of 
                         these offsets cannot be estimated reliably from the AgriSAR 
                         amplitude data, and complex data should be supplied as a standard 
                         product. No sound basis for inter-image comparison has been found. 
                         As a result, only qualitative conclusions about the multi-temporal 
                         behaviour of the backscatter from crops are possible. Cereals and 
                         sugar beet appear to display different backscatter signatures with 
                         incidence angle. The statistical separability of wheat and sugar 
                         beet varies with time and incidence angle; the separability of 
                         wheat and barley varies with time but not incidence angle. 
                         Backscatter from cereals appears to display greater spatial 
                         variability than from sugar beet. Individual fields show great 
                         apparent variation in their multi-temporal behaviour, much of 
                         which can be attributed to the sample statistics, but appears to 
                         be real at least for winter wheat.",
                label = "6325",
        urlaccessdate = "01 maio 2024"
}