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Re: AI-GEOSTATS: Surfer 6.04

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  • Bambang Trisasongko
    Hi Eva, I usually saw the problem in remote sensing image analysis. From my experience, the difference is based on different use of floating point data types.
    Message 1 of 3 , Feb 20, 2002
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      Hi Eva,

      I usually saw the problem in remote sensing image analysis. From my
      experience, the difference is based on different use of floating point data
      types. As you may refer on standard textbook on programming languages,
      there are slightly difference between languages in handling floating point
      data.
      Another problem is coding mathematical/statistical equations. Solving
      equations may be constructed in different ways. I usually refer to some
      numerical analysis book such as John Rice, Don Knuth or if you using
      specific programming languages, there are versions of Numerical Recipes by
      Press et al.
      I hope it can help.

      Regards,

      Bambang




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    • Eva Pierce
      Hello, Has anyone used or encountered Surfer 6.04 by Golden Software? I have been using Surfer to interpolate grids of points using Kriging and other methods,
      Message 2 of 3 , May 8, 2002
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        Hello,

        Has anyone used or encountered Surfer 6.04 by Golden Software? I have
        been using Surfer to interpolate grids of points using Kriging and other
        methods, and comparing results to a program I wrote that does the same.
        The results are slightly different, and I would like to know how much of
        that difference can be attributed to floating-point errors. Does anyone
        know the nature of Surfer's floating-point arithmetic (precision etc),
        and/or the algorithms it uses for solving Kriging matrix equations?

        Eva



        [Non-text portions of this message have been removed]
      • Eva Pierce
        Thanks for your advice, all. I downloaded the Surfer 8 demo software and found that Surfer 8 s results are much closer to mine than Surfer 6. This, Mr.
        Message 3 of 3 , May 13, 2002
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          Thanks for your advice, all. I downloaded the Surfer 8 demo software and
          found that Surfer 8's results are much closer to mine than Surfer 6.
          This, Mr. McCarn's recollection, and a cursory look at Surfer 6's memory
          usage during processing all indicate that Surfer 6 uses 4-byte floating
          point arithmetic, even though Golden Software tech support claims
          otherwise.

          I wish I could nail down why my results are still different than Surfer
          8 by up to 5%. I think it is probably floating point error that
          accumulates over the many calculations required to solve for Kriging
          weights, so I plan to look at some numerical methods books and do some
          testing etc. If you have experience with floating-point problems and
          would like to share, I'm all ears!

          Eva

          -----Original Message-----
          From: Bambang Trisasongko [mailto:bht@...]
          Sent: Wednesday, February 20, 2002 2:58 AM
          To: Eva Pierce
          Cc: ai-geostats@...
          Subject: Re: AI-GEOSTATS: Surfer 6.04

          Hi Eva,

          I usually saw the problem in remote sensing image analysis. From my
          experience, the difference is based on different use of floating point
          data
          types. As you may refer on standard textbook on programming languages,
          there are slightly difference between languages in handling floating
          point
          data.
          Another problem is coding mathematical/statistical equations. Solving
          equations may be constructed in different ways. I usually refer to some
          numerical analysis book such as John Rice, Don Knuth or if you using
          specific programming languages, there are versions of Numerical Recipes
          by
          Press et al.
          I hope it can help.

          Regards,

          Bambang




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          * As a general service to the users, please remember to post a summary of any useful responses to your questions.
          * To unsubscribe, send an email to majordomo@... with no subject and "unsubscribe ai-geostats" followed by "end" on the next line in the message body. DO NOT SEND Subscribe/Unsubscribe requests to the list
          * Support to the list is provided at http://www.ai-geostats.org
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