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RE: [ai-geostats] Optimal rain gauge network

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  • Rühaak, Wolfram
    Hi Craig, ... I am quite sure that there are methods to estimate an optimal station-setup (probably colleagues with more experience will answer), but I want to
    Message 1 of 6 , Jan 3, 2006
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      Hi Craig,

      > -----Original Message-----
      > From: Craig von Hagen [mailto:craigvonhagen@...]
      > Hi All,
      >
      > I have an interesting problem to solve, I hope
      > someone could help me.
      >
      > We are working on flood early warning in Somalia
      > and we have the following situation.
      >
      > We have an existing network of manual rain gauges
      > that we receive on a monthly basis with daily
      > readings taken manually by a person in the field.
      > These however can be unreliable.
      >
      > We have an option to install automatic rain gauges
      > that would give us an accurate measurement of
      > rainfall per day. We would like to use
      > geo-statistics to then give a prediction and error
      > surface and then use these surfaces to evaluate how
      > accurate and reliable our existing manual network
      > is.
      >
      > Is there a way to calculate the optimal network
      > (number and location) for the automatic stations so
      > that we get a reliable prediction surface which we
      > can then use to evaluate our manual network?
      > [...]
      > Thanks and regards
      > Craig

      I am quite sure that there are methods to estimate an optimal station-setup (probably colleagues with more experience will answer), but I want to point out an other thing:
      rainfall is mostly not uniform distributed. The topography has a major impact, also differences of the land cover can result in differences of the (micro - meso scale) climate. There are probably also coastal effects.

      I think, that it would be necessary to take this also into account. Which makes the calculation of number and place of the new stations more difficult.

      Hope this helps a little bit, cheers Wolfram
    • Gerald van den Boogaart
      Dear Craig von Hagen, If you install a network of automated gauges, which is dense enough to make a map to check the manual gauges, sure enough it makes the
      Message 2 of 6 , Jan 4, 2006
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        Dear Craig von Hagen,

        If you install a network of automated gauges, which is dense enough to make a
        map to check the manual gauges, sure enough it makes the manual network
        superfluous.

        And such network would not really help evaluating the operators:
        * Anyway if the measurement of a manual gauge is underestimated systematically
        by the interpolated surface I would first suspect a difference in
        microclimate to be the origin of that and not a bad operator.

        * If the variation of the measurement is underestimated by the kriging error I
        would suspect an additional measurment error in the manual measurements or a
        ill specified variogramm before blameing the operator.

        If you would like to check a manual network you might consider two options:

        1) Install mobile automatic gauges next to manual ones and check by simple
        comparison (however you need to consider wether the operator should be
        allowed to know that he is controlled currently). Than move the mobile gauge
        to the next station.

        2) To check single operators you can run cross-validation with the existing
        manual network: estimate a prediction and a kriging error from all stations
        but the one to be checked and compare. You need to add the nugget effect of
        the semivariogram to the kriging error to get the variance of
        Prediction-Measurement.

        Best regards,
        Gerald v.d. Boogaart




        Am Dienstag, 3. Januar 2006 14:53 schrieb Craig von Hagen:
        > Hi All,
        >
        > I have an interesting problem to solve, I hope
        > someone could help me.
        >
        > We are working on flood early warning in Somalia
        > and we have the following situation.
        >
        > We have an existing network of manual rain gauges
        > that we receive on a monthly basis with daily
        > readings taken manually by a person in the field.
        > These however can be unreliable.
        >
        > We have an option to install automatic rain gauges
        > that would give us an accurate measurement of
        > rainfall per day. We would like to use
        > geo-statistics to then give a prediction and error
        > surface and then use these surfaces to evaluate how
        > accurate and reliable our existing manual network
        > is.
        >
        > Is there a way to calculate the optimal network
        > (number and location) for the automatic stations so
        > that we get a reliable prediction surface which we
        > can then use to evaluate our manual network?
        >
        > I am the most familiar with the ArcGIS GeoStatistical
        > Analyst.
        >
        > Thanks and regards
        > Craig
        >
        >
        > Craig von Hagen
        > FAO - GLCN/Africover/SWALIM Projects
        > PO Box 30470-00100
        > Nairobi, Kenya
        >
        > Tel: +254 20 444 3331
        > Fax: +254 20 444 1993
        >
        > www.africover.org
        > www.glcn.org; www.glcn-lccs.org
        > www.faoswalim.org
        >
        >
        >
        > ___________________________________________________________
        > To help you stay safe and secure online, we've developed the all new Yahoo!
        > Security Centre. http://uk.security.yahoo.com

        --
        -------------------------------------------------
        Prof. Dr. K. Gerald v.d. Boogaart
        Professor als Juniorprofessor fuer Statistik
        http://www.math-inf.uni-greifswald.de/statistik/

        office: Franz-Mehring-Str. 48, 1.Etage rechts
        e-mail: Gerald.Boogaart@...
        phone: 00+49 (0)3834/86-4621
        fax: 00+49 (0)89-1488-293932 (Faxmail)
        fax: 00+49 (0)3834/86-4615 (Institut)

        paper-mail:
        Ernst-Moritz-Arndt-Universitaet Greifswald
        Institut f�r Mathematik und Informatik
        Jahnstr. 15a
        17487 Greifswald
        Germany
        --------------------------------------------------
      • Craig von Hagen
        Hi Gerald, Thanks very much. However maybe it was not clear in my first email. We are not just interested in checking the gauge readers but also in: 1.
        Message 3 of 6 , Jan 9, 2006
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          Hi Gerald,

          Thanks very much. However maybe it was not clear in my
          first email. We are not just interested in checking
          the gauge readers but also in:

          1. Connecting Somalia to the Global Observing
          System
          2. Feeding into the GTS to allow for validation
          of RFE data (and corrections used in the RFE 2.0
          algorithm).
          3. Using the data collected to provide data on
          storm duration and intensity (at present we only get
          24 hour readings)
          4. Real time flood forecasting and drought
          monitoring.

          The use of the rain gauges for checking/validating
          manual readings is an added benefit.

          I am also looking into the WMO methods for
          establishing a gauge network.

          So far responses received from the list for optimal
          gauge location inlcude: stratification by elevation -
          assumption being rain increases with height (although
          not really the case here as we have rainfall on the
          coast).
          - wieghting locations in terms of their contribution
          to flooding
          - adding gauges at locations where their is most
          uncertainty
          - taking into account topogrpahy, slope and coastal
          effects.

          Further inputs are welcome...

          Regards
          Craig


          --- Gerald van den Boogaart
          <boogaart@...> wrote:

          > Dear Craig von Hagen,
          >
          > If you install a network of automated gauges, which
          > is dense enough to make a
          > map to check the manual gauges, sure enough it makes
          > the manual network
          > superfluous.
          >
          > And such network would not really help evaluating
          > the operators:
          > * Anyway if the measurement of a manual gauge is
          > underestimated systematically
          > by the interpolated surface I would first suspect a
          > difference in
          > microclimate to be the origin of that and not a bad
          > operator.
          >
          > * If the variation of the measurement is
          > underestimated by the kriging error I
          > would suspect an additional measurment error in the
          > manual measurements or a
          > ill specified variogramm before blameing the
          > operator.
          >
          > If you would like to check a manual network you
          > might consider two options:
          >
          > 1) Install mobile automatic gauges next to manual
          > ones and check by simple
          > comparison (however you need to consider wether the
          > operator should be
          > allowed to know that he is controlled currently).
          > Than move the mobile gauge
          > to the next station.
          >
          > 2) To check single operators you can run
          > cross-validation with the existing
          > manual network: estimate a prediction and a kriging
          > error from all stations
          > but the one to be checked and compare. You need to
          > add the nugget effect of
          > the semivariogram to the kriging error to get the
          > variance of
          > Prediction-Measurement.
          >
          > Best regards,
          > Gerald v.d. Boogaart
          >
          >
          >
          >
          > Am Dienstag, 3. Januar 2006 14:53 schrieb Craig von
          > Hagen:
          > > Hi All,
          > >
          > > I have an interesting problem to solve, I hope
          > > someone could help me.
          > >
          > > We are working on flood early warning in Somalia
          > > and we have the following situation.
          > >
          > > We have an existing network of manual rain gauges
          > > that we receive on a monthly basis with daily
          > > readings taken manually by a person in the field.
          > > These however can be unreliable.
          > >
          > > We have an option to install automatic rain gauges
          > > that would give us an accurate measurement of
          > > rainfall per day. We would like to use
          > > geo-statistics to then give a prediction and error
          > > surface and then use these surfaces to evaluate
          > how
          > > accurate and reliable our existing manual network
          > > is.
          > >
          > > Is there a way to calculate the optimal network
          > > (number and location) for the automatic stations
          > so
          > > that we get a reliable prediction surface which we
          > > can then use to evaluate our manual network?
          > >
          > > I am the most familiar with the ArcGIS
          > GeoStatistical
          > > Analyst.
          > >
          > > Thanks and regards
          > > Craig
          > >
          > >
          > > Craig von Hagen
          > > FAO - GLCN/Africover/SWALIM Projects
          > > PO Box 30470-00100
          > > Nairobi, Kenya
          > >
          > > Tel: +254 20 444 3331
          > > Fax: +254 20 444 1993
          > >
          > > www.africover.org
          > > www.glcn.org; www.glcn-lccs.org
          > > www.faoswalim.org
          > >
          > >
          > >
          > >
          >
          ___________________________________________________________
          > > To help you stay safe and secure online, we've
          > developed the all new Yahoo!
          > > Security Centre. http://uk.security.yahoo.com
          >
          > --
          > -------------------------------------------------
          > Prof. Dr. K. Gerald v.d. Boogaart
          > Professor als Juniorprofessor fuer Statistik
          > http://www.math-inf.uni-greifswald.de/statistik/
          >
          > office: Franz-Mehring-Str. 48, 1.Etage rechts
          > e-mail: Gerald.Boogaart@...
          > phone: 00+49 (0)3834/86-4621
          > fax: 00+49 (0)89-1488-293932 (Faxmail)
          > fax: 00+49 (0)3834/86-4615 (Institut)
          >
          > paper-mail:
          > Ernst-Moritz-Arndt-Universitaet Greifswald
          > Institut für Mathematik und Informatik
          > Jahnstr. 15a
          > 17487 Greifswald
          > Germany
          > --------------------------------------------------
          >
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        • Thomas M. Parris
          Craig, You may wish to take a look at what FEWS-NET has been doing in Southern Africa. It look very similar to what you have in mind. See
          Message 4 of 6 , Jan 9, 2006
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            Craig,

            You may wish to take a look at what FEWS-NET has been doing in Southern
            Africa. It look very similar to what you have in mind. See
            http://www.sadc-hazards.net/. Particularly,
            http://gisdata.usgs.net/sa_floods/aspmap/. I know there are several
            technical papers that provide additional detail. One such paper is at
            http://www.isprs.org/commission1/proceedings02/paper/00030.pdf. You might
            want to get in touch with the authors to see if there are any others.

            With best regards,
            Tom Parris
            ------------------------------------------------------------
            Thomas M. Parris
            Director of Sustainability Programs
            ISciences, LLC
            61 Main Street, Suite 200
            Burlington, VT 05401 USA

            Tel: +802-864-2999 http://www.isciences.com/
            Fax: +617-344-2580 http://www.terraviva.net/
            Email: parris@...
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