Loading ...
Sorry, an error occurred while loading the content.

1935Re: [ai-geostats] Kriging along streams

Expand Messages
  • Edzer J. Pebesma
    Feb 24, 2005
    • 0 Attachment
      Noemi, the idea of transforming to a one-dimensional situation,
      distance along river, was the first one I got. Then, I rejected
      it because it will not work for river networks; it will for a
      single sections without joints though. Space-time modelling may
      be complicated by the fact that there will be a strong
      correlation with future observations downstream, but not with
      observations upstream because water flows down; this may call
      for another translation of space-time using flow speed to get
      to a space-time coordinate system where the usual models make
      sense.
      --
      Edzer

      Noemi Barabas wrote:
      > Dear Oscar,
      >
      > It sounds like you need kriging in a single dimension. If so, I think what
      > you need to do is a kind of coordinate transformation, for example using
      > river mile as your distance vector. You would also need to pay attention to
      > the dates of the samples. Variation in time might obscure spatial trends
      > along the river's course if you just have a few sampling events at different
      > times for the stations.
      >
      > If you have data in space as well as time, there are several methods for
      > space-time interpolation. Constructing correlograms for data vs time on
      > paired stations could give you an idea of what constitutes a data pair for
      > kriging purposes in terms of the time lag between them. Methods will differ
      > depending on whether it is the time or space dimension that is more densely
      > sampled.
      >
      > References on techniques include the following:
      >
      > For straightening rivers (which might be more involved than you need):
      >
      > Barabas, N., Goovaerts, P. and P. Adriaens. 2001. Geostatistical assessment
      > and validation of uncertainty for three-dimensional dioxin data from
      > sediments in an estuarine river. Environmental Science & Technology, 35(16):
      > 3294-3301.
      >
      > For space-time data:
      >
      > Pebesma and de Kwaadsteniet (1997) Mapping spatial and temporal variation of
      > groundwater quality in the Netherlands. In GeoENVI - Geostatistics for
      > Environmental Applications, eds., Soares et al, pp. 139-151. Kluwer
      > Academic Publishers, Netherlands.
      >
      > Kyriakidis and Journel (1999) Geostatistical space-time models: A review.
      > Mathematical Geology (not sure which volume etc.)
      >
      > Heuvelink et al (1996) Spatio-temporal kriging of soil water content. In
      > Geostatistics Wollongong '96, eds Baafi and Schofield. pp. 1020-1030.
      > Kluwer Academic Publishers,Netherlands.
      >
      >
      > Noémi
      >
      >
      >
      > -----Original Message-----
      > From: oscar garcia [mailto:osgarcia@...]
      > Sent: Thursday, February 24, 2005 11:56 AM
      > To: ai-geostats@...
      > Subject: [ai-geostats] Kriging along streams
      >
      >
      > Dear list members,
      >
      > I want to perform kriging of water quality indicators
      > measured in stations along a river course, so Can you
      > help me with references about kriging along streams in
      > a river basin?? is there software to perform this kind
      > of analysis???
      >
      > Thanks in advance for your help,
      >
      > Oscar Javier García-Cabrejo
      > Master in Hydrosystems, Civil Engineering Department
      > Pontificia Universidad Javeriana
      > Bogota, Colombia
      > South America
      >
      > _________________________________________________________
      > Do You Yahoo!?
      > La mejor conexión a internet y 25MB extra a tu correo por $100 al mes.
      > http://net.yahoo.com.mx
      >
      >
      >
      >
      > ------------------------------------------------------------------------
      >
      > * 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

      --
      Edzer
    • Show all 5 messages in this topic