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Thread: Pixels disappear when I change rgb bands

  1. #1
    graham langley-edwards
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    Default Pixels disappear when I change rgb bands

    Hi, I have raster layer of a Landsat 1 satellite image. I need to change the band allocation to be Red: Band 4, Green: Band 3, Blue: Band 2. However, when I do this many pixels disappear from the layer. If I change it back to the original band allocation, the pixels come back. I have not been able to find any info on this particular problem in the forums. Any suggestions would be much appreciated.

    Thanks,

    Graham

  2. #2
    Patrick Taurman

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    Default Re: Pixels disappear when I change rgb bands

    What do you mean by "disappear"? If you use the Identify tool after changing bands do you still see the pixel values? Can you post a screenshot of before and after. Also try changing the ArcMap background to something other than white (something very obvious), and then change the bands, do you see the ArcMap background color where pixels existed?

    Patrick

  3. #3
    graham langley-edwards
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    Default Re: Pixels disappear when I change rgb bands

    Hi Patrick,

    Thanks for your reply. I mean that the pixels return a "No Data" value. The areas where the pixels disappear are all black, so white is the best background. If I change the bands, many of the pixels return, but there are missing pixels in different areas, and the white background is clearly visible. I will post a before and after screen shot when I return to the lab tomorrow.

    Thanks again for your help,

    Graham

  4. #4
    graham langley-edwards
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    Default Re: Pixels disappear when I change rgb bands

    Here are the screen shots of before and after. The first one (NormalPixels) is before, has a rgb band combination of 1,2,3 and has no missing pixels (the few missing pixels at the top are intentional). The second one (NoDataPixels) is after, has a rgb band combination of 4,3,2 and has several areas of missing pixels. It looks like all of the areas of missing pixels are in black areas, but I don't know how that could help. If anyone has any suggestion, I would appreciate it.

    Thanks,

    Graham
    Attached Thumbnails Attached Thumbnails Click image for larger version

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Name:	NoDataPixels.jpg‎
Views:	28
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ID:	13895  

  5. #5
    Patrick Taurman

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    Default Re: Pixels disappear when I change rgb bands

    What version of ArcGIS are you using, and what is the format of the raster?

  6. #6
    graham langley-edwards
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    Default Re: Pixels disappear when I change rgb bands

    I'm using ArcGIS 10 and the format for the raster is Grid Stack 7.x... Still haven't been able to resolve this issue. If anyone has any ideas. I would really appreciate it.

    Thanks,

    Graham

  7. #7
    Patrick Taurman

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    Default Re: Pixels disappear when I change rgb bands

    Hi Graham,

    I haven't had any problems like this with 10. What service pack are you using? Do you have a small sample dataset you can post here to test with? If you can't post it here, I would contact Support, so we can get a some data to test with.

    Patrick

  8. #8
    graham langley-edwards
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    Default Re: Pixels disappear when I change rgb bands

    Patrick,

    I am using service pack 2, but I'm not sure what data to post. I tried posting what I believe are the files for each of the four bands for the data layer in question, mostly .adf files, but it said that they were invalid files. Is there some other way I could send you the data, or some other data you could use? Thanks again or your help...

    Graham

  9. #9
    Patrick Taurman

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    Default Re: Pixels disappear when I change rgb bands

    Hi Graham,

    I sent you a message with my email address, and a colleagues email address, as I will be leaving the country tomorrow for two weeks.

    Patrick

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