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Hi Greg, I finally got some time to revisit the color bar labeling issue for "Fog" products created using: Fog = 150 + 10(T10.7 - T3.9) Or, in IMGOPER terms: IMGOPER RTIMAGES/GE-IR RTIMAGES/GE-39 MYDATA/IMAGES.3000 FUNC=ADD COEF=1 -1 ACON=150 MCON=10 UNIT=TEMP where: RTIMAGES/GE-IR -- GOES-EAST 10.7um infrared RTIMAGES/GE-39 -- GOES-East 3.9um infrared Since IMGOPER is not producing a correct calibration block for this channel difference, I performed "calibrations" using sets of images for diverse times of the day (e.g., 20081026.1945, 20071027.0945, 20071027 1415): - chose points in the difference product that represented large ranges in brightness - interrogated the original 10.7um and 3.9um images to get the temperatures at the same geographical locations as in the difference product The three images I chose this morning showed the _exact_ same equivalence between output brighness in the difference product and temperature difference in the input products. Representative numbers (for 20071027.1415) are: 10.7um 3.9 um Difference BRIT TEMP BRIT TEMP BRIT del(T) ---- ----- ---- ----- ---- ------ 183 235.0 170 245.0 50 -10.0 76 292.0 69 295.5 115 -3.5 75 292.5 60 295.5 120 -3.0 75 292.5 70 295.0 125 -2.5 94 283.0 91 284.5 135 -1.5 69 295.5 69 295.0 150 0.0 147 256.5 151 254.5 170 +2.0 105 277.5 115 272.5 200 +5.0 This relationship is represented by the following formula: del(T) = (5/50) BRIT - 15 You can generate a McIDAS stretch table that reflects this relationship as follows: <in a McIDAS session> SU INI IRDELT PRD TEMP SU MAKE IRDELT -10 5 50 200 You would use this stretch to annotate your resultant image as follows: SF 1 ERASE IMGDISP MYDATA/IMAGES.3000 LAT=0 72 MAG=-4 EU=IMAGE BAR SU=IRDELT LINT=1 NOTEs: - it is unknown to me if this relationship is valid for platforms other than GOES-East (GOES-12). My gut feeling is that it should be for GOES-West (GOES-11) and GOES-South (GOES-10) since the calibrations for the IR channels are identical for these three platforms. - I will be looking at the source code for IMGPROBE (imgprobe.pgm) to see if I can figure out why a usable/correct PRD calibration is not being created. Please let me know if you have questions on anything listed above. 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: OKG-462913 Department: Support McIDAS Priority: Normal Status: Closed