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Hi Julia, re: > I am using McIDAS to access unidata2.ssec.wisc.edu. There are 3 groups: > GOESEAST, EAST, and WEST. I found out that the area files are different > among these three groups. That is correct. The EAST and WEST datasets are composed of multibanded images. The GOESEAST dataset is composed of single-banded images. Please note that all of the IR images in the GOESEAST dataset are identical to the ones sent in the Unidata-Wisconsin IDD datastream (UNIWISC). They are also available from the RTIMAGES dataset on several servers. The only image that is significantly different is the 1 km Visible one. The Visible images sent in the Unidata-Wisconsin datastream have all been blown-down to an effective 4 km resolution. > For example, area files of band 1 from EAST or > WEST are GVAR/RAW file with 2 bytes/pixel, while the area file of band 1 > from GOESEAST is VISR/BRIT file with 1 byte/pixel. Can anyone explain the > difference among them? The EAST and WEST datasets are populated by GOES ingest machines. The images are all 10-bit and are oversampled in the element dimension. The images in the GOESEAST dataset are created from images in the EAST and SOUTH datasets (SOUTH is hosted on goessouth.unidata.ucar.edu; it contains realtime images from GOES-10 which is now being used to scan South America). The GOESEAST images have the element oversampling removed (MAG=1 -2) and have been converted in to 8-bit (1-byte) images. > When using IMGDISP EAST/CONUS.0 1 BAND=1, the satellite image was not > displayed. This is strange. Perhaps you tried loading the image when one would not expect Visible data because it was dark? I just tried loading the VIS band (BAND=1) from the latest EAST/CONUS image and I also got a blank. The IR images were fine, however. This will take some more investigation on my part. > But IMGDISP GOESEAST/WH-4KVIS.0 1 BAND=1 can. Is it because > EAST/CONUS.0 is a GVAR/RAW file? No. The use of the different types of images in McIDAS is transparent. > When using AXFORM to convert EAST/CONUS area file to ASCII, is the digital > count converted directly from the 2-byte raw data? Or from the 10-bit > value? The two-byte data _IS_ the 10-bit data. To answer your question, however, I must point out that AXFORM works on local AREA files. If the AREA file you are dumping values from has 10-bit data, then AXFORM converts the counts from the 10-bit data. If the AREA file you are working with contains 1-byte data, then AXFORM is converting the 1-byte data. > In the document of > McIDAS data structure, it specifies that GVAR data has 10 bits formatted > as: > > |0|x|x|x|x|x|x|x|x|x|x|0|0|0|0|0| Correct. Images tagged as GVAR should contain 10-bit data. Images tagged as VISR should contain 1-byte data. > Thanks, No worries. 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: XQI-115437 Department: Support McIDAS Priority: Normal Status: Closed