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Re: [ai-geostats] Optimal rain gauge network

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  • 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 1 of 6 , Jan 9, 2006
      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
      > >
      > >
      > >
      > >
      >
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      > --
      > -------------------------------------------------
      > 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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