User Manual - pancroma

19. Image Subsetting________________________________________________________________Many users will wish to process and pan sharpen entire scenes. However thereare many reasons to process image subsets, that is, part of a satellite image file.Often only a portion of a large image is of interest. Even when the entire imageis needed, it is much more convenient to determine the optimum imageprocessing parameters (see sections below) iteratively while experimenting withsubset data, and then afterwards apply those settings to the larger file, thussaving a lot of computing time. One problem is that the pan sharpening and gapfilling processes require precisely matched sets of images: for example three orfour band files plus the panchromatic image with row and column sizes in thecorrect proportion. PANCROMA TM is able to produce such matched sets usingits subsetting algorithms.You can subset four band data sets in any supported file format for 2X file sets(where panchromatic band rows and columns are 2 times (or 2X-1) thecorresponding band row and column sizes). You can also subset four filesubsets created by the Digital Globe file extraction utility in GeoTiff format (sincethis is the only output format supported by the utility.)To begin the subsetting process, Select ‘File’ | ‘Open’ as above. Successivelyselect the input band images in the order: blue; green; red. In addition, open oneadditional file: the associated panchromatic image. This will have an …nn80…(GeoTiff) or ‘…_B80.L1G’ (L1G) suffix if it is a Landsat file or a .._p10_.. suffix if itis a SPOT file.IMPORTANT NOTE: if you are processing Landsat L1G images, it is necessaryto download the metadata file into the same directory as the band andpanchromatic files. This is because the L1G flat binary format is not capable ofincluding image metadata itself. The companion metadata file has the suffix‘…_MTL.L1G.htm’. Note: the metadata file is available in different formats. Besure to select the HTML version with the file suffix .mht’. (If PANCROMA TM doesnot find this file , you will be prompted to enter the row and column count datamanually.) These values will always be labeled ‘lines’ and ‘samples’ and will looksomething like this in the metadata files:PRODUCT_SAMPLES_PAN = 15781PRODUCT_LINES_PAN = 13961PRODUCT_SAMPLES_REF = 7891PRODUCT_LINES_REF = 6981IMPORTANT NOTE: Some browsers may add control characters when savingthe .mht file. These characters may prevent PANCROMA TM from successfully37