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RE: AI-GEOSTATS: Kriging a stream surface

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  • Warren Schlechte
    Maureen, I believe we met in Savannah a couple of years ago. If you don t mind, could you send me any responses you get as a summary? Such seems useful to
    Message 1 of 4 , May 2, 2002
      Maureen,

      I believe we met in Savannah a couple of years ago. If you don't mind,
      could you send me any responses you get as a summary? Such seems useful to
      know - how to best deal with boundary conditions. It would seem from my
      neophyte position that such would be easy to do. First, you don't provide
      any data from the adjacent land. Hence the estimation of the variogram won't
      take anything but stream readings into account. Second, when you provide a
      grid to estimate over, only provide points that lay within the stream. One
      item you will want to consider is how you portray your grid. Since a stream
      is a self-contained entity, I would think that distance should be portrayed
      as distance within the stream, distance as the water flows, not distance as
      the crow flies. Another aspect you may wish to consider is that streams
      have direction. Hence, it would seem unusual (with the exception of large
      inflows) for downstream sites to ever have an effect on upstream sites.
      This would suggest all sites should only look upstream for temperature
      information. The final item that comes to mind quickly is the influence of
      inflow. These will be sources of different temperatures than exist in the
      main stream basin. As such, it would seem that any major inflows should be
      measured.

      Hope that my thought help, and that you get the help you need from this
      group.


      Warren Schlechte

      -----Original Message-----
      From: ai-geostats-list@... [mailto:ai-geostats-list@...] On Behalf
      Of Maureen Walsh
      Sent: Wednesday, May 01, 2002 9:35 PM
      To: ai-geostats@...
      Subject: AI-GEOSTATS: Kriging a stream surface

      << File: vcard.vcf >> I am interested in using kriging to interpolate
      temperature surfaces for
      a stream that I work on, based on data from fixed point temperature
      loggers along the length of the stream. However, I am unsure if it is
      possible to constrain the analysis within the stream boundaries. I was
      wondering if anyone with experience conducting these types of analyses
      would have any suggestions about how to address this problem.
      Thank you very much,
      Maureen Walsh


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    • Noemi Barabas
      Dear Maureen, I have dealt with the same problem. The basic approach is to transform your coordinates as Warren suggested. If you only have one measurement
      Message 2 of 4 , May 2, 2002
        Dear Maureen,

        I have dealt with the same problem. The basic approach is to transform
        your coordinates as Warren suggested. If you only have one measurement
        per transect, than it is as simple as working with distance from a set
        point such as the last or first sampling point, and your variogram and
        kriging is one-dimensional. If you need a 2-dimensional transformation,
        than it gets much more complicated. There are different approaches
        possible, such as normalizing to distance from one bank or from the
        center of flow. Then, regardless of how wide the stream is, two points
        1/3 of the way into the stream will have the same lateral coordinates. You
        also have to account for angles to the bank or center line.

        I used a grid generation approach in my case. You can use commercial
        software or write your own code. I settled for the latter, the commercial
        software (Gridgen from Pointwise) is for much more complicated problems.

        Look at this reference for a general description:
        Barabas N, Goovaerts P, Adriaens P (2001) Geostatistical Assessment and
        Validation of Uncertainty for Three-Dimensional Dioxin Data from Seidments
        in an Estuarine River. Environ. Sci. Technol. 35, 3294-3301.

        Noemi
        Noemi Barabas

        PhD Candidate
        The University of Michigan
        Dept. Civil and Environmental Engineering
        1351 Beal Avenue (13 EWRE)
        Ann Arbor, MI 48109-2125
        Phone: (734) 615-5905


        On Thu, 2 May 2002, Warren Schlechte wrote:

        > Maureen,
        >
        > I believe we met in Savannah a couple of years ago. If you don't mind,
        > could you send me any responses you get as a summary? Such seems useful to
        > know - how to best deal with boundary conditions. It would seem from my
        > neophyte position that such would be easy to do. First, you don't provide
        > any data from the adjacent land. Hence the estimation of the variogram won't
        > take anything but stream readings into account. Second, when you provide a
        > grid to estimate over, only provide points that lay within the stream. One
        > item you will want to consider is how you portray your grid. Since a stream
        > is a self-contained entity, I would think that distance should be portrayed
        > as distance within the stream, distance as the water flows, not distance as
        > the crow flies. Another aspect you may wish to consider is that streams
        > have direction. Hence, it would seem unusual (with the exception of large
        > inflows) for downstream sites to ever have an effect on upstream sites.
        > This would suggest all sites should only look upstream for temperature
        > information. The final item that comes to mind quickly is the influence of
        > inflow. These will be sources of different temperatures than exist in the
        > main stream basin. As such, it would seem that any major inflows should be
        > measured.
        >
        > Hope that my thought help, and that you get the help you need from this
        > group.
        >
        >
        > Warren Schlechte
        >
        > -----Original Message-----
        > From: ai-geostats-list@... [mailto:ai-geostats-list@...] On Behalf
        > Of Maureen Walsh
        > Sent: Wednesday, May 01, 2002 9:35 PM
        > To: ai-geostats@...
        > Subject: AI-GEOSTATS: Kriging a stream surface
        >
        > << File: vcard.vcf >> I am interested in using kriging to interpolate
        > temperature surfaces for
        > a stream that I work on, based on data from fixed point temperature
        > loggers along the length of the stream. However, I am unsure if it is
        > possible to constrain the analysis within the stream boundaries. I was
        > wondering if anyone with experience conducting these types of analyses
        > would have any suggestions about how to address this problem.
        > Thank you very much,
        > Maureen Walsh
        >
        >
        > --
        > * To post a message to the list, send it to ai-geostats@...
        > * 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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