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This paper describes a method for monitoring winter wheat growth using multi-temporal TerraSAR-X dual-polarimetric data. Six TerraSAR-X HH/VV images were collected in Hokkaido, and the temporal responses to the winter wheat fields were analyzed. The height, moisture content and dry matter of the crops were measured at nearly the same time as TerraSAR-X data was acquired, and the relationships between these parameters and SAR data, including sigma naught and coherence, were studied. Quadratic relationships between the crop height and sigma naught were observed for HH polarization. The determination coefficient was 0.73 and the model had an RMS error of 0.17 dB for the validation data. Coherence is expressed as a regression equation with two explanatory variables: crop height and elongation. Next, the determination coefficient of 0.69 was observed for HH, while the RMS error of coherence was 0.01 for the validation data. The possibility of using the co-polarization ratio of TerraSAR-X to estimate the vegetation's water content was also analyzed and a determination coefficient of 0.70 was obtained. The results confirm that X-band SAR data possess great potential for the development of an operational system for monitoring wheat growth.
