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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
    • Chris Hlavka
      Craig - I m not an expert with geostatistics and related software, but here are a couple of general principals to consider: 1) In statistical experimental
      Message 2 of 6 , Jan 3, 2006
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        Craig - I'm not an expert with geostatistics and related software,
        but here are a couple of general principals to consider:

        1) In statistical experimental design design, the greatest
        improvement in estimates are achieved by adding points at the
        locations with the most uncertainty.

        2) Define your optimization carefully. Instead of minimization a
        simple sum of squares, weight locations in terms of their
        contribution to flooding. A hydrological model can be helpful in
        defining this - using soil type maps and local slopes computed from
        digital elevation data.

        Chris

        >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
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        >
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        >Signoff ai-geostats


        --
        ***************************************
        Chris Hlavka
        NASA/Ames Research Center 242-4
        Moffett Field, CA 94035-1000
        (650)604-3328 FAX 604-4680
        Christine.A.Hlavka@...
        ***************************************
      • 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 3 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 4 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
            > --------------------------------------------------
            >
            > > * By using the ai-geostats mailing list you agree
            to
            > follow its rules
            > ( see
            > http://www.ai-geostats.org/help_ai-geostats.htm )
            >
            > * To unsubscribe to ai-geostats, send the following
            > in the subject or in the body (plain text format) of
            > an email message to sympa@...
            >
            > Signoff ai-geostats






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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 5 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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