A method for detecting change in coral reef using pan-sharpened satellite images

摘要

A method was developed for global monitoring of temporal change of coral reef using pan-sharpened color images with higher accuracy and lower cost. The method consisted of 3 blocks; image co-registration for removing complex discrepancy due to parallax among original color image and panchromatic one, pan-sharpening with preserving color information, and change detection with suppressing noise such as sea waves. The method was successfully applied to an actual FORMOSAT2 multi-temporal data set. After removing the parallax between multi-spectral band images and panchromatic one, the spatial resolution of multi-spectral images was improved from 8 × 8 m~2 to 2 × 2 m~2 in the following pan-sharpening block. The pan-sharpening was performed by replacing brightness component of the original multi-spectral pixel with the panchromatic pixel density. In order to normalize the recording gain and offset, the brightness component was estimated by using a linear polynomial model whose coefficients were determined by applying a multiple regression analysis. Linear shapes of density scatter diagram of each spectral band between pan-sharpened density and original one indicated that the pan-sharpened spectral information was perfectly preserved. The change detection successfully detected some temporal changes with suppressing noise. The method was applicable to other data sets having lower resolution multi-spectral images and panchromatic one covering all spectral bands.