User Manual - pancroma

PANCROMA TM has a utility for converting Landsat 7 band file DNs to TOAreflectances. The procedure for carrying out such a conversion is as follows:Conversions must be made one Landsat 7 band file at a time. Open a band fileby selecting ‘File’ | ‘Open’. (PANCROMA TM can input Landsat TIFF and L1Gformat files) Then select ‘PreProcess’ | ‘Compute Radiometric Corrections’ |‘Compute Landsat 7 TOA Reflectance’. The TOA Reflectance Data Form willbecome visible. This form will ask you to input certain parameters from themetadata file that accompanies each Landsat 7 scene. These parameters areneeded to compute and render (if desired) the TOA data. The requiredparameters are the band number, the solar elevation angle, the acquisition dateand a scale factor (to make the image display properly.)Note that the Landsat 7 algorithm actually wants the solar zenith angle, which is90 o minus the solar elevation angle. However the solar elevation angle, not thezenith angle is archived in the metadata file so input the solar elevation angleand PANCROMA will take care of the conversion. PANCROMA TM will notconvert the acquisition date from the Gregorian calendar to Julian days. Youmust do this yourself by either counting on your fingers or alternatively using theNASA link on the PANCROMA TM Help menu (http://wwwair.larc.nasa.gov/tools/jday.htm)labeled “Launch NASA Ordinal Date Converter”.TOA reflectance is also used for cloud masking and an explanation of the SolarElevation Angle and Acquisition Date is given in the Cloud Masking section ofthis manual. Additional required parameters include the Landsat band number(this is needed because the sensor gain and offset values are not the same forall Landsat bands) and a graphics image scale factor. In addition, the form hascheck boxes for writing the TOA reflectance data to file and for rendering it as animage.PANCROMA TM gives you two options for saving your reflectance or radiancedata: flat binary file or GeoTiff. You can elect to save your file to disk in flatbinary format by checking the check box on the TOA Reflectance form when itbecomes visible. Afterward, you will be prompted for an output file name, withthe suffix ‘bin’, denoting a binary data file. PANCROMA TM will output the data inflat binary form using IEEE 32-bit FLOAT (little endian) format. The output filewill be ((ROWS by COLUMNS * 4) ) + 8) bytes in size. The extra 8 bytes resultfrom the number of rows and number of columns that precede the FLOAT data.These are output as 4 byte integers, again in little endian format. The filestructure is shown schematically below.181