Newly launched sensors such as Terra ASTER or Terra/Aqua MODIS have channels to cover short wave infrared (SWIR) which is sensitive or effective to detect water condition on the land surface. In this study, firstly, a set of normalized indices including normalized difference vegetation index (NDVI), normalized difference soil index (NDSI) and normalized difference water index (NDWI), collectively called NDXI, were newly introduced by extending the idea of NDVI using SWIR channels. Secondly, their behavior were investigated for a variety of eleven spectral signatures observed at the ground level. It was found that NDXI were highly correlated with the existence of vegetation, soil and water. Thirdly, the compatibility of typical optical sensors were evaluated using the spectral response of ASTER, AVHRR, ETM and MODIS. Finally the atmospheric effects were evaluated using radiative transfer simulation under a variety of aerosol, visibility, topography and sun-target-sensor geometry.
In this study, spatio-temporal patterns of continuous paddy fields were examined using the patterns observed in metrics calculated for six month of MODIS over Japan. Four analytical approached were used; calculation of temporal mean, maximum and minimum layers for selected metrics showing significant spatial variability of channel 1, 2, NDVI; linear discriminant for input into the un-mixing analysis was derived from the same multi-temporal metrics used for the classification product using ASTER; the continuous percentage of paddy field was generated based on un-mixing technique with the training data derived from the above mentioned ASTER data. The derived metrics were not sensitive to time of year or the seasonal cycle and can limit the inclusion of atmospheric contamination. The comparison of 250m MODIS product with the past efforts on AVHRR, SPOTVEGETATION and MODIS sensors, and statistics by IRRI showed that the finer resolution and its un-mixing played a crucial role in depicting the paddy field cover over Japan.
Many camera calibration methods for a non-metric camera have been proposed. Some of them use a set of control points distributed on the 2D plane instead of a set of control points distributed in the 3D space. However there are few reports to demonstrate effectiveness of camera calibration using a set of 2D control points. Therefore, we conducted a numerical simulation in order to examine the effectiveness of camera calibration using a set of 2D control points. In the simulation calibration results obtained by three methods using a set of 2D control points were compared with those obtained by the method using a set of 3D control points with the depth of the distribution from 1/5 to 1/20 of the object distance. Evaluation of calibration results was performed by differences of image distortions calculated at all pixels on the image between the obtained image distortion model and the setup one. The simulation results indicate that the calibration methods using a set of 2D calibration points can provide a reliable set of camera parameters.