User Manual - pancroma

64. Processing Huge Files and File Size Limitations________________________________________________________________PANCROMA TM was written and optimized to process standard Landsatmultispectral image sets. The program manages system resources to effect anefficient balance between file size and processing speed for the size of dataassociated with Landsat multispectral and panchromatic band files. Files that aresomewhat larger than standard Landsat can be successfully processed. Thelargest file that you will be able to process will be dependent on your computerresources, particularly your installed RAM. Since PANCROMA TM requiresinternal storage that is proportional to the input file sizes, limitations exist that areimposed by the Windows operating system. These are described in a WhitePaper entitled “Pan Sharpening Huge Satellite Image Files” available atwww.PANCROMA.com.If your data set exceeds the capability of PANCROMA TM and your computer,your only real recourse is to subset the input data. Since operations on a singlegrayscale image require only an 8-bit color model, quite large grayscale imagescan be displayed and subsetted. If “out of memory” processing errors occur, trysubsetting your data one file at a time. This requires loading the first band file byselecting ‘File’ | ‘Open’ and then ‘Band Combination’ | ‘Subset Images’ | ‘SubsetSingle Image’.Since PANCROMA TM keeps track of your row and column coordinates inbetween subset runs, this is pretty easy. You just subset your first band andsave it, then select ‘Close Graphics Windows and Reset’ and then repeat thesubsetting process for the second band. The latitude and longitude coordinatesand row and column coordinates from the first subsetting operation will beretained in the Subset Data Entry text boxes, so you just select ‘Accept PixelEntries’ and then ‘Enter’ and the second band will be subsetted to the samecoordinates as the first band. You can repeat this as often as desired.Note that although the panchromatic band has the same latitude and longitudecoordinates as the multispectral bands, it does not have the same row andcolumn coordinates. These must be computed manually based on the size ratiobetween the multispectral bands and the panchromatic band. For Landsat, theratio is 1:2. You can multiply the coordinates when subsetting Landsat data setsby clicking on the ‘2X’ button before clicking ‘Accept Pixel Entries’. In this casethe row and column coordinates will be automatically updated for easiersubsetting.302