The data ignore value is not used when applying gain and offset in this case. The tool does not accept an input mask either. However, applying the gains and offsets do not effect adjacent pixels so the background data ignore values should all have the same value after you apply them. After using the tool, you can then create and apply a mask to set the background value to the value of your choice. To convert the data type from double to float, you can use the Stretch data tool or Band Math: float(b1) then use Map variable to input file to convert all bands to float. Are you unable to use the Radiometric Calibration tool? This applies gains and offsets from metadata and can prepare the data so that it is ready for input to FLAASH.

Thanks, I use the following code to add 'data ignore value' for the input data, It successufly remoe the back 0 value when processing. IF (metadata.HasTag ('data ignore value')) THEN BEGIN metadata.UpdateItem, 'data ignore value', 0.0 ENDIF ELSE BEGIN metadata.AddItem, 'data ignore value', 0.0 ENDELSE The second question: the output data from the the envitask'RadiometricCalibration' is BSQ format, the FLAASH dose not support the BSQ format. So what should i do to change the output data format in the envitask''RadiometricCalibration'' I want to use this code Task.Output_Interleave='BIL' but the envitask ''RadiometricCalibration'' does not support this method. Thanks so much for your help

No, that routine does not support the keyword for converting interleave. The tasks have been modularized in many ways so you would need to export a new raster with the interleave you desire. For example: raster=e.OpenRaster(file) newfile=e.gettemporaryfilename('dat') raster.export,newfile,'envi',interleave='bip' However, there is no FLAASH API. This is a UI tool only. You could use Quac instead. http://www.harrisgeospatial.com/docs/...