User Manual - pancroma

Calibration requires multiplication of each grayscale image digital number (DN)by the Absolute Calibration Factor and then dividing it by the EffectiveBandwidth. After calibration, each of the grayscale bands must be rescaled toreasonable brightness levels using the same scale factor for each image. I wrotethe code required for the calibration and scaling and incorporated it into the latestversion of PANCROMA. To calibrate an image you must first obtain the AbsoluteCalibration Factor (absCalFactor) and Effective Bandwidth (effectiveBandwidth)from the .IMI file that accompanies each data set. Note that each of the eightbands has its own calibration coefficients. Each band must be calibrated using itsown calibration coefficients but scaled using a common scale factor.To calibrate, open a single grayscale image using the 'File|Open' menu selection.After opening the file, select 'Pre Process'|'Calibrate WorldView2 Band'. A datainput form will be displayed. Insert the calibration coefficients for the band youare calibrating into the text boxes on the data input form. You can use the defaultscale factor, or input one of your own. The optimum scale factor can becomputed as:Scale Factor = SUM(absScaleFactor)/SUM(effectiveBandwidth)WhereSUM(absScaleFactor)= (absCalFactor1 + absCalFactor2 + absCalFactor3)AndSUM(effectiveBandwidth = (effectiveBandwidth1 + effectiveBandwidth2 +effectiveBandwidth3)After calibrating the band and panchromatic images using the default scale factorof '4', I saved them to disk. I then applied a proportional histogram stretch to eachof the bands in turn and saved them again. (Note: it is not necessary to stretchthe panchromatic band as it will be automatically histogram matched during thepan sharpening operation.)RapidEye Top of Atmosphere ReflectancePANCROMA TM can compute TOA Reflectance for RapidEye band files. Theprocedure is nearly the same as for Landsat band files. Conversions must bemade one RapidEye band file at a time. First, decompose the bundled RapidEyefive-band TIFF file into individal 16-bit bandfiles. Next, open a band file byselecting ‘File’ | ‘Open’. Then select ‘PreProcess’ | ‘Compute RadiometricCorrections’ | ‘Compute RapidEyeTOA Reflectance’. The TOA Reflectance DataForm will become visible. This form will ask you to input the parameters that areneeded to compute and render (if desired) the TOA data. The Solar ElevationAngle and Acquisition Date are required.196