2009 Volume 25 Issue 1 Pages 27-34
Due to the aging of agricultural worker population, Japanese agriculture is relying on inexperienced young farmers. This study has been carried out to give them the appropriate information on the growth condition of the crops through remote sensing technique. Measuring system composed of two digital cameras, optical filters and brightness sensors was set in an agricultural rice field of Toyama Prefectural Agricultural, Forestry and Fisheries Research Center through March to October of 2007. Seasonal change of normalized difference vegetation index (NDVI) has been calculated from the measured by the fixed-point digital cameras. Length, number of stems and SPAD value of the stems were measured about once a week throughout the measuring period. The NDVI calculated from the digital camera images showed rapid growth in the early growth periods of rice. This should be caused mainly by the oblique measurements by the cameras. Although the measurements by fixed-point cameras are very important as the “ground truth” experiments for comparison with the satellite data, it has been shown that we have to pay enough attention to the effects of the camera angles and so on. The digital camera images were converted into two dimensional frequency domain images by Fast Fourier Transformation (FFT). The time dependence of the average pixel value in a specific frequency region has shown a similar tendency with rice length in the early periods of the rice phenology. This implies the importance of the fixed-point camera measurements for estimation of growth condition even with the frequency domain information other than the spectrographic results.
