Unwanted movements during image recording usually cause problems for optical imaging systems onboard Earth Observation satellites. The major effect of these movements is the degradation of image quality by smearing and distortion. The aim of this paper is to provide estimates of the blur-caused MTF of an isolated CCD detector element as a result of linear motion to evaluate the impact of such blur, that may be experienced operationally, on the whole system MTF of the Alsat-1B imager. The estimates are made on ground prior to launch and include effects caused by linear motion of the spacecraft relative to the earth and exclude effects of motion caused by mechanical vibration or platform drift. Those estimates are of great importance as part of system level analysis which can help restoring the degraded image.
To date, several pan-sharpening methods have been proposed in the literature. However, conventional Pan-sharpening
processes are based on color separation (RGB decomposition for example) of color (spectral) images resulting in
significant loss of color information. The aim of this work is to investigate the potential of hypercomplex numbers
representation of color images, in particular Quaternion model, for satellite images pan-sharpening. Quaternion model
allows color images to be handled as a whole, rather than as color-separated components. That is, the values of the color
components (R, G and B for example) of each pixel of a color image are represented as a single pure quaternion valued
pixel. The proposed fusion method is based on Quaternion intensity-hue-saturation (QIHS) transform and consists of
three steps. First, the color (spectral) image is represented as a pure quaternion image to take into account its particular
nature. Then, the IHS transform is applied to the pure quaternion image resampled at the scale of panchromatic (Pan)
image. Finally, the image fusion process is done by IHS-based component substitution. The efficiency of the proposed
method is tested on Quickbird dataset. A comparative evaluation among the proposed technique and the standard IHSbased
method available in the commercial software ENVI is then conducted.
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