Spectral and radiometric distortion evaluation of pan-sharpened XS imagery obtained from compressed XS and pan data

This work reports about an original application concerning lossy compression of multispectral (XS) and panchromatic (Pan) images collected by spaceborne platforms. Generally, the former is a set of three or four narrow-band spectral images, while the latter is a single broadband observation imaged in the visible and near-infrared wavelengths. Since high resolution spectral observations having high SNR are difficult to obtain, and especially to transmit, the Pan image, having resolution typically four times that of XS, but slightly lower SNR, is added to the XS data and used with the main purpose of expediting both visual and automatic identification tasks, possibly through an integration (merge) with the lower resolution XS data. Whenever XS data at the same resolution of the Pan data and with adequate SNR were hypothetically available on board, the bottleneck of downlink to receiving stations would impose severe limitations in the bit rate, so that a lossy compression would be mandatory. The consequence of the loss of information is a distortion, both radiometric and especially spectral, which may be easily quantified.