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>From: Darren Gallant <address@hidden> >Organization: UCAR/JOSS >Keywords: 200207111918.g6BJIGa29261 McIDAS AREA calibation Darren, >What exactly is a pre-calibrated image? An image that has a specific -- fixed -- conversion from brightness counts to a calibrated unit. For instance, the IR and WV images in the Unidata-Wisconsin datastream have a fixed, two slope, linear relationship between brightness values and temperature. >I know Tom discussed this with me >before, but I can't recall the specifics. Both the SSEC and CSU data have >calibration blocks. Are they used when the image is displayed? The display is simply a mapping of internal "raw" counts to values that can range from 0 to 255. When you interrogate the image using IMGPROBE, the calibration block -- if it exists -- is used to convert the raw counts to calibrated values like temperature, radiance, albedo, etc. Tom