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Last Post 25 Nov 2022 11:40 AM by  Karen Kowalewsky
Statistics Issues
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Karen Kowalewsky



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Posts:9
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24 Oct 2022 10:23 AM
    I have an image that ran successfully through QUAC and when I try to run a SAM classification I get a "Zero Array" error message. I'm using ENVI 5.6.2 looking at Planet Scope data. I run a simple band statistics and get the following:

    Dims: Full Scene (30,223,820 Points)

    Basic Stats Min Max Mean StdDev
    Band 1 1 12885 328.570124 270.797651
    Band 2 1 11342 333.476376 334.043302
    Band 3 1 11260 500.696536 372.898197
    Band 4 1 11467 585.325001 403.536483
    Band 5 1 14718 563.031181 446.156745
    Band 6 1 13842 496.661480 488.603188
    Band 7 1 17270 1198.019299 586.159480
    Band 8 1 13301 2480.427232 1252.710369

    There are no zero values. Then I run al full band statistics and get the following:

    Dims: Full Scene (30,223,820 points)

    Basic Stats Min Max Mean Stdev Num Eigenvalue
    Band 1 0 12885 328.5211 270.7906 1 2100365.0463
    Band 2 0 11342 333.4159 334.0329 2 683809.8925
    Band 3 0 11260 500.5996 372.9165 3 42464.7513
    Band 4 0 11467 585.2082 403.5716 4 6612.7311
    Band 5 0 14718 562.9266 446.1655 5 2702.7361
    Band 6 0 13842 496.5695 488.5905 6 1207.4291
    Band 7 0 17270 1197.8048 586.2794 7 761.5955
    Band 8 0 13301 2479.9441 1253.0105 8 461.4861

    With the same dimensions and the same number of points and now I have a minimum of 0.

    Why the difference and is this the source of the error?

    Thanks,
    Karen Kowalewsky

    MariM



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    Posts:2396
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    25 Oct 2022 06:40 AM
    When you say you run simple vs full stats, do you mean the 'Quick Stats' you can calculate from the Layer Manager vs the Band Statistics tool?
    In any case, my guess is that a data ignore value was set on some pixels after quac processing.
    Can you post the error message you receive?

    Karen Kowalewsky



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    Posts:9
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    25 Nov 2022 11:40 AM
    I re-ran QUAC and also reset my ROI categories. Apparently for whatever reason one of the original ROIs had zero pixels. Once I corrected that issue everything worked.
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