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Hi Carol, re: > Thanks for your patience here. No worries. Stretches are a bit difficult to get one's head around. re: > I was under the impression that the stretch > table was mostly necessary for selecting the proper units outside of > brightness. This and the mapping of unit to brightness. re: > The values in SU would ultimately define the BAR as well. Yes, and the purpose of the example I sent was to show how to get the BAR labels to read in FT when the unit of the calibrated value is M. re: > I > thought the enhancement table (EU) is the only command that would actually > change the display (color of the pixels). Yes, sort of. An enhancement maps display brightness to colors. If you change the mapping of calibrated unit to brightness with a stretch, you are changing the brightness, and the visual result will be a change in color. re > For instance, here is another > example with two different SU but the same EU. > > [mcidas@typhoon ~]$ su.k TABLE L2-CTH > BREAKPOINTS STORED IN TABLE : L2-CTH.ST > INPUT OUTPUT > ----- ------ > 0 0 > 20000 255 > CALIBRATION TYPE : ABIN > CALIBRATION UNITS : M > BAND NUMBER : -1 > INTERPOLATION TYPE: LIN > su.k: DONE > [mcidas@typhoon ~]$ su.k TABLE L2-CTH-TEST > BREAKPOINTS STORED IN TABLE : L2-CTH-TEST. > INPUT OUTPUT > ----- ------ > 10000 0 > 20000 255 > CALIBRATION TYPE : ABIN > CALIBRATION UNITS : M > BAND NUMBER : -1 > INTERPOLATION TYPE: LIN > su.k: DONE > > Then I have attached two images. These two images have the exact same > pixels/colors, but the BARs are different. Light blue maps to 16,000 meters > in one image versus 12,000 meters in the other image. The range you specified in the first stretch is not much different from the mapping of calibrated value (cloud top height) to brightness that is defined in the 'abincalb.inc' file, so there should not be much in the way of difference in brightness (brightness -> color via an enhancement) when using it or not. The second stretch, on the other hand should have a noticeable effect since it should be making all pixels for which calibrated values are less than 10000 black and then ranging the brightnesses (again, colors via the enhancement) over a subset of the possible calibrated values. Hmm... I think I now understand the source of the confusion. The changing of mapping of calibrated unit to brightness in the stretch will only take effect when the stretch is specified on the IMGDISP command line via the SU=<stretch> keyword. Simply specifying a stretch in the BAR command without doing so in the IMGDISP command will have no effect on the mapping of calibrated value to brightness because that has to be done on image load. I just tried creating a stretch like your second one, using it in an IMGDISP load, and my display is black. I have to think that this is a telling me that there is something wrong either with the stretch, or with the code that is doing the conversion during the IMGDISP. re: > In any case, it's probably just best to stretch over all values for this > example, so the 0 to 20000 range BAR is the correct one (0 to 65000 for > feet). I suppose if I did SU MAKE TEST 10000 20000 127 255, that would work > as well? I'll need to look into the stretch use with Level 2 products more before I can comment further. This will likely be later today as I have some other things going on this morning, sorry. Cheers, Tom -- **************************************************************************** Unidata User Support UCAR Unidata Program (303) 497-8642 P.O. Box 3000 address@hidden Boulder, CO 80307 ---------------------------------------------------------------------------- Unidata HomePage http://www.unidata.ucar.edu **************************************************************************** Ticket Details =================== Ticket ID: KFB-284893 Department: Support McIDAS Priority: Normal Status: Open =================== NOTE: All email exchanges with Unidata User Support are recorded in the Unidata inquiry tracking system and then made publicly available through the web. If you do not want to have your interactions made available in this way, you must let us know in each email you send to us.