High-speed and Precise Geometric Correction for GMS-5 S-VISSR Data

Since the GMS-5 observes the earth very widely and frequently, its S-VISSR data are very useful not only for meteorology but also for sea surface and land surface temperature analysis, heat and water budget analysis and the various kinds of database generated from the S-VISSR data will contribute the understanding of earth environmental change. In order to process GMS-5 S-VISSR data immediately after reception and provide academic researchers the geometrically corrected data useful for the time series analysis, a high-speed and precise geometric correction method is described. For precise geometric correction, residual errors are acquired by matching the S-VISSR image pieces to their corresponding ground control point templates on image coordinate, and the affine coefficient is calculated using the errors. For fast computation, the output image of the map coordinate is divided into small blocks. Each latitude-longitude of four corners on a small window is converted to line-pixel in image coordinate by systematic geometric transformation and affine transformation is carried out toward the line-pixel for precise geometric correction. In the case of internal points excluding four corners in the small window, each correspondence of line-pixel and latitude-longitude is calculated by hi-linear interpolation using correspondences of the four corners for speeding up the geometric correction. As the result, the accuracy measured at low altitude points is about 0.5 pixels in average and within 2 pixels, and the processing time is about 6 minutes. The product is open for public use via the Internet.