User Manual - pancroma

22. Pan Sharpening Transformation Methods________________________________________________________________PANCROMA TM provides four transformation algorithms for pan sharpening: HSI,AJISANE, Brovey and SPECTRAL. These are offered as choices when youselect the ‘Pan Sharpening’ menu item. The HSI algorithm is considered astandard. This method works best for Landsat 8 data. PANCROMA TM can pansharpen three multispectral bands with the panchromatic band. Alternatively byselecting ‘Pan Sharpening’ | ‘HSI Based Transforms’ | ‘Pan Sharpen from RGBComposite’ you can sharpen an RGB color composite image with thepanchromatic band.The basic HSI is improved by the XIONG and ENHG five file algorithms, whichuse the near infrared (NIR) band in addition to the blue, green and red bands tocreate the pan sharpened image. These, especially XIONG generally producesuperior results when pan sharpening with the Landsat 7 panchromatic band.ENHG can also provide improved results but can often over compensate andcreate an image with overstated green tones.The AJISANE method also works well with Landsat 7 as it uses the NIR band tocorrect spectral distortions introduced by the nature of the Landsat panchromaticband. It is especially useful for images where the XIONG method producesunwanted artifacts as described in Section 14.The Fast HSI algorithm is also included. The Fast HSI algorithm has beendescribed by Giannini and others 3 . This algorithm generally produces results verysimilar to that of the standard HSI algorithm. Unfortunately the algorithm does notlive up to its name. While it may arguably be faster in theory, it is slower and takesup more RAM than the standard HSI algorithm in practice. It can sometimesproduce less noisy results especially on ocean surfaces than the standard HSI so itis included for that reason.PANCROMA TM also includes a 16-bit version of the Fast HSI algorithm. This optionuses the full 16-bit dynamic range when pan sharpening Landsat 8 scenes. After pansharpening you can choose to save the color RGB image in the standard 8-bitformats. In addition you can save the band files in 16-bit GeoTiff format by selecting‘File | ‘Save Subset Images’ | ‘GeoTiff’.The Brovey method is a bit less expensive with respect to computational timeand memory resources. It often produces a darker image that needs brighteningand often contrast improvement to produce acceptable images. Experiment withall to see which gives the better result for your image. (Note that some of thedefault image processing settings will be altered when processing with Brovey. It3 APPLICATION OF IHS PAN-SHARPENING TECHNIQUES TO IKONOS IMAGES, Massimiliano Basile GianniniPasquale Maglione , Claudio Parente, CNR - Institute of Atmospheric Pollution Research Monterotondo (Rome)50