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Thread: recalculating parameters of the standard deviational ellipse

  1. #1
    Susanne Janschitz
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    Default recalculating parameters of the standard deviational ellipse

    Hi colleagues,
    I am working with ArcGIS 10.0 (SP 4) and are trying very hard to recalculate the XStdDist and YStdDist values for the Standard Deviational Ellipse ArcGIS offers me by hand (using Excel).
    I was able to reproduce the angle of rotation but not more. The values I get for the axes of the ellipse do not differ from each other and are completely different from the ArcGIS results.
    I used the formulars in the ArcGIS Help but somewhere I am doing a fatal mistake.
    Could anybody help me with a hint? I am desperately looking for a solution.
    Thanks so much in advance
    Susanne

  2. #2
    Dan Patterson

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    Default Re: recalculating parameters of the standard deviational ellipse

    and what are the result summaries between the two?
    Geomatics, Carleton University, Ottawa, Canada
    http://obidangis.blogspot.ca/

  3. #3
    Susanne Janschitz
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    Default Re: recalculating parameters of the standard deviational ellipse

    Thanks for your reply. The sum is simply about the doubled value since they are almost the same.
    I have attached the excel sheet to my mail because its hard to explain in words.
    I am sure I made a simple but essentail mistake and although trying to solve I am some kind of "blind".
    Thanks
    Susanne
    Attached Files

  4. #4
    Susanne Janschitz
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    Default Re: recalculating parameters of the standard deviational ellipse

    Dear colleagues,
    I did find the mistake - the formulas contain a mistake - instead of a minus there seems to be a plus in the formula for the standard dev of the y-axis. Additional there is a scaling factor implemented.
    Thanks
    Susanne

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