Speaking of SURFER and GIS, check out SurfLink at
http://www.certaintech.com/surflink.asp which leverage the best of
both technologies.

- David Ward
www.earthwardconsulting.com

--- In hydrologymodel@..., "Xavier Coello-Rubio"
<xcoellor@y...> wrote:
>
> Hello Tejaswi
>
> The problem is that the method that you are using doesn't fit for
> chemical parameters, because those values could be from decimals
to
> thousands. I Strongly recommend you to use Krigging method, BUT
using
> the appropiete variogram. The best software could be SURFER or an
> Arcview extention for krigging (you can find out in the internet).
>
> Regards
>
> Xavier COELLO-RUBIO
> UNESCO-IHE
> The Netherlands
>
>
> --- In hydrologymodel@..., Maribeth Milner
> <mmilner1@u...> wrote:
> >
> > Tejaswi,
> >
> > There are many algorithms for interpolating data. Some
> are "exact" (in
> > that they return the value of the input data) and some
> are "inexact".
> >
> > The Surfer (http://www.goldensoftware.com/) documentation
> provides this
> > list of exact and inexact interpolators...
> >
> > Exact:
> > Inverse Distance to a Power (no smoothing function)
> > Kriging (no specified nugget effect)
> > Nearest Neighbor
> > Radial Basis Function (no R2 specified)
> > Modified Shepard's Method (no smoothing factor)
> > Triangulation with Linear Interpolation (TIN)
> > Natural Neighbor
> >
> > Inexact:
> > Inverse Distance to a Power (with smoothing factor)
> > Kriging (with error nugget)
> > Polynomial Regression
> > Radial Basis Function (with R2 specified)
> > Modified Shepard's Method
> >
> > Note... the ability to return input values may or may not be
> related to
> > surface accuracy. To test accuracy, hold out (don't use) a few
> well
> > positioned data points and compare those values with their
> predicted
> > values. All interpolators have problems at the edges of data
sets,
> so be
> > sure to collect extra data (outside of your study area) to avoid
> this problem.
> >
> > Also, interpolators generally describe local variability or
global
> > variability - not both. The exceptions are geostatistics and
> radial basis
> > functions.
> >
> > Surfer has been a favorite interpolator package, but ESRI's
> Geostatistical
> > Analyst extension (in ArcGIS) is also very good. Besides having
> both
> > radial basis functions and geostatistical functions - it
provides
> surface
> > error analysis tools that produce both graphic and numeric
> descriptors.
> >
> > ESRI has a free online course that covers this extension
> > (http://campus.esri.com/campus/catalog/index.cfm?
> CFID=17792502&CFTOKEN=22787
> > 414 "Introduction to ArcGIS 9 (or 8) Geostatistical Analyst")
that
> will
> > get you started. Looks like this month's free online seminar
> (offered 3
> > times on Jan 26th) will also cover this extension
> (http://campus.esri.com/).
> >
> > Good luck,
> >
> > Maribeth
> >
> > At 04:15 PM 1/10/2006 +0000, you wrote:
> >
> > >Hello members,
> > > I am using ArcView 3.2a (demo version) to generate
contour
> maps for
> > > different physico chemical parameters of groundwater samples.
The
> > > contours are being generated by making use of the point
> interpolation
> > > method. While generating these maps from the database created,
i
> am
> > > encountering this problem. The problem is, many of the
contours
> are
> > > displaying negative values. There are no negative values in
the
> database
> > > and moreover no field in the database is left blank. The
minimum
> value
> > > for any of the parametes is zero. Eventhough for some of the
> parameters
> > > there are not even zero values, the negative contour values
are
> being
> > > displayed.
> > > Any one knowing the solution for this problem is kindly
> requested
> > > to help me in this regard.
> > >
> > > Thanks in advance
> > >
> > > Tejaswi
> >
>