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Greetings,

the daily rainfall data and the associated DEM for the book project
are available at our anonymous ftp site.

ftp java.ei.jrc.it

cd /pub/ai-geostats/austria/

The files are named

au30apr.csv
au1may.csv
au2may.csv
au3may.csv
au4may.csv
au5may.csv
au6may.csv
au7may.csv
au8may.csv

for the rainfall and

austdem.grd

for the Digital Elevation Model.

Please refer to the book project at

http://java.ei.jrc.it/rem/gregoire/BOOK/book.html

for more information.

Regards



Gregoire

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About Patrick's mail problem:

The mailing list server is running under Majordomo which does not deal well
with nonstandard headers in mail messages. This can be one of the reasons of
getting "blank" messages sent to ai-geostats. The poster can try to put a few
blank lines between the headers and the content of his message.

If the problem persists, please contact me.

Regards


Gregoire

<gregoire.dubois@...>
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Greetings,

Is there anything wrong (perhaps with my screen) so that I could not read
the content of this posting which was being posted twice.

Thanks
Abedini


On Wed, 2 Apr 1997, Patrick Wong wrote:

>
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>

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Special Issue of
International Journal of Systems Research and Information Science

              Spatial Data Analysis and Modelling

                         Guest Editors

              Dr. T.D. Gedeon (tom@...)
              Department of Information Engineering
           School of Computer Science and Engineering

               Dr. P.M. Wong (pm.wong@...)
                Centre for Petroleum Engineering

                The University of New South Wales
                   Sydney, NSW 2052, Australia

In much science and engineering practice today, there is an increasing
demand for techniques which are capable of spatial data analysis. Spatial
data analysis is the analysis and modelling of data distributed in space,
and has various applications in fields including: geographical information
systems (GIS) such as forest, rainfall, environmental modelling and
assessment; geoscience such as hydrology and petroleum reservoir modelling;
ecology, epidemiology, and many other disciplines which need to characterise
and predict data distributed in space.

Researchers in all areas of spatial data analysis are invited to contribute
to this special issue which will attempt to cover much of the current
state-of-the-art in spatial data analysis. Topics will be a good mix of
the following areas:

1) Artificial intelligence (e.g. neural nets, fuzzy logic, expert systems)
2) Geostatistical modelling (e.g. inverse distance, splines, lattice & point
    data analyses)
3) Data integration and visualisation (software-focussed)
4) Case histories

Acceptance will be based on the overall significance and appropriateness of
the reported material, as well as the quality of presentation. Use of very
specialised technical jargons is not recommended in order to suit the wide
readership of the journal. The focus should be on the usefulness, practical
aspects of the technique, and how the theory is adapted for field applications.
All material should be original and are not submitted or published elsewhere
while under editorial consideration.

                               Paper submission

Three copies of all manuscripts are required on paper. An abstract of no more
than 150 words should be provided. The length of the text should not exceed
5,000 words. All papers will be internationally reviewed by two experts in
the area. The journal notes for contributors and paper submission format can be
found at:

           http://www.petrol.unsw.edu.au/staff/srisformat.html

The deadline for paper submission is 1 July 1997. Notification of acceptance
will be sent out around 1 October 1997.

Please notify your intention to submit to the guest editors before 1 May 1997.
All papers and future correspondence should be sent to:

                                Dr. P.M. Wong
                       Centre for Petroleum Engineering
                       The University of New South Wales
                          Sydney, NSW 2052, Australia

                           Email: pm.wong@...
                               Fax: +61-2-9385 5936

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Hello all. I've run up a problem (doubt) while doing nearest-neighbour
statistics. Davis explains in his book 'Statistics in Geology'
how to check if a set of points is randomly distributed, but
I would like to check if a set of points is ramdomly distributed
in relation to a set of lines. I was wondering if the point test
could be used considering point-to-nearest-line distances instead.

Thanks in advance.

Peter

University of Cordoba
Spain, EU
Email: peter.caruana@...
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Hello everybody!

I have several data sets on land use, and I believe they are basically
anisotropic
at least for the distances (up to 40 km) for which I want to compute
correlograms.

I would like to test the hypothesis of anisotropy before making computations
under this assumption.

So far I could not find any hypothesis test for this.
Can anybody give me a hint on references about this topic?


F. Javier Gallego
JRC  tp. 440
21020 Ispra (Varese)
Italy

tel: 39.332.785101
fax: 39.332.789074
e-mail: javier.gallego@...








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how did I get this e-mail?

Did it come to me on purpose?   Is this part of the April fools joke?

Wish I could help - but I can't and no offense to anyone, but if I am on
someone's list, could you take me off?

Thanks
  ----------
From: Javier Gallego
To: 'ai-geostats@...'
Subject: GEOSTATS: testing anisotropy
Date: April 9, 1997 05:24

Hello everybody!

I have several data sets on land use, and I believe they are basically
anisotropic
at least for the distances (up to 40 km) for which I want to compute
correlograms.

I would like to test the hypothesis of anisotropy before making
computations
under this assumption.

So far I could not find any hypothesis test for this.
Can anybody give me a hint on references about this topic?


F. Javier Gallego
JRC  tp. 440
21020 Ispra (Varese)
Italy

tel: 39.332.785101
fax: 39.332.789074
e-mail: javier.gallego@...








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On Wed, 9 Apr 1997, Javier Gallego wrote:

> Hello everybody!
>
> I have several data sets on land use, and I believe they are basically
anisotropic
> at least for the distances (up to 40 km) for which I want to compute
correlograms.
>
> I would like to test the hypothesis of anisotropy before making computations
> under this assumption.
>
> So far I could not find any hypothesis test for this.
> Can anybody give me a hint on references about this topic?
>

Do you refer to directional anisotropy? If so, then
directional semivariograms (or correlograms) should be
compared. Deutsch and Journel (1992) GSLIB ox. Uni. Press could
be an start point. Are you planning to interpolate or are you just
testing hypothesis?

Agus


Dr. Agustin Lobo
Instituto de Ciencias de la Tierra (CSIC)
Lluis Sole Sabaris s/n
08028 Barcelona SPAIN
tel 34 3 330 2716
fax 34 3 411 0012
alobo@...
alobo@...



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Dear Colleagues,

Operations Research Unit Committee of the Society for Mining, Metallurgy,
and Exploration, Inc. has started planning the Operations Research sessions
for the 1999 SME Annual Meeting that will be held between March 1-4 in
Denver, Colorado.  Tentatively, two OR sessions are planned.  The titles of
the sessions are:
         1. OR I - Geostatistics, and
         2. OR II - Mining Systems Analysis
The latter will encompass deterministic and probabilistic mathematical
models, simulation, expert systems, neural networks, fuzzy sets, and the
like.  Would you please take a few moments and let me know if you are
planning to submit an abstract?  If you do, please let me also know the
preliminary title of your abstract.  The intent to submit an abstract will
not be binding on your part.  You are welcome to make suggestions for
session topics or titles as the foregoing are tentative.  This information
will help us finalize the number and the topics of the OR sessions in
Denver.  My apologies if you receive duplicate copies of this message from
different list servers.  Thanks.

_______________________________________________________________________

Dr. Ahmet Unal                Phone:  (573) 341-4838
Dept. of Mining Engineering   Fax:    (573) 341-6934
University of Missouri-Rolla  WWW: http://www.umr.edu/~unala/
Rolla, MO 65409-0450          E-Mail: unala@...
_______________________________________________________________________

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Just get me the 400 MB when it comes available.

	 Bob
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Dear fellow colleagues,

XV INQUA 1999 CONGRESS
3 - 11 August 1999 Durban, South Africa

The Congress will open with a one-day symposium devoted to the Congress
theme:  "Environmental background to hominid evolution in Africa".

Thereafter symposia and workshops will address key issues in Quaternary
studies including glaciation, palaeohydrology, loess, neotectonics,
palaeoclimate, palaeopedology, tephrochronology, human palaeoecology,
terrestrial carbon, shorelines, vegetation history and stratigraphy.

A range of pre- and post-congress excursions is offered to important sites in
Southern Africa countries.

The first circular and pre-registration forms are available on the Congress
Internet Homepage at the following address:  inqua.geoscience.org.za

Alternatively, the circular may be obtained from Mrs E Aucamp, PO Box 798,
Silverton PRETORIA, 0001 South Africa Fax: +27-12-8411221, E-mail:
eaucamp@...

For further information, please contact the Secretary-General:  PO Box 61,
Cape Town 8000 South Africa, Fax:+27-21-246716, E-mail: mavery@...

Kind regards
Elzanne Aucamp
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------- Blind-Carbon-Copy

X-Mailer: exmh version 2.0beta 12/23/96
to: wolfe@...
Subject: Recent changes in subscribe policy and other administrivia
X-uri: http://www.ems.psu.edu/~wolfe
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Date: Mon, 14 Apr 1997 13:52:11 -0400
From: Jeff Wolfe <wolfe@wegener>


Hi folks,

Due to a recent rash of forged subscriptions to our list, I've upgraded the
software that runs this list to the latest release of Majordomo. Among other
things, the list now requires a confirmation from new subscribers before they
are added to the list, which should prevent any more forged subscriptions.

Unfortunately, I have no way to sort through the current subscriber list and
remove the poor folks who have forged subscriptions.

If you get this message and you do not want to be on the ai-geostats, or the
ai-geostats-digest mailing list:

please send a message to "majordomo@..."

with

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in the message body and you will be removed from the list.

To the ai-geostats subscribers: Sorry for the intrusion.. We now return you to
your regularly scheduled programming.. :)

- -Jeff


------- End of Blind-Carbon-Copy

This message is to make sure I didn't break Majordomo when I changed the
subscribe policy last week.

I think I found the problem. If this makes it through, things should be OK.

-Jeff



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********************************************************

                   POST-DOC Position

********************************************************

The Marine Environment Unit (ME) of the Space Application
Institute (SAI) of the Joint Research Centre (JRC) of
the European Commission is looking for Candidates for a

         -- Post-Doc Position (2 years) --

for:

THE DEVELOPMENT OF GENERIC ELEMENTS FOR A DECISION
SUPPORTING SYSTEM FOR COASTAL ZONE MANAGEMENT,
INTEGRATING REMOTE SENSING AND OTHER DATA SOURCES

Aim of Work to be performed:

To improve the use and application of remote sensing and
other Earth observation data and to derive higher value
products.

The Candidate will participate in the following activities:

1) to collect, validate and classify relevant information
    about coastal areas;

2) to identify existing activities and processes of relevance;

3) to define the Objectives of the System to be designed;

4) to design the expert system module (integrating remote
    sensing and other data);

5) to design the decision module (including Multi-Criteria
    Technique);

6) to implement the System;

7) to execute pilot studies.

It is expected that the Candidate will make significant
contributions to positions 4) to 7).

The Candidate should have experience preferably in the
following areas (in priority order):

1) Decision support systems and related methodologies;
    geo-information systems (GIS ...) and related topics
    (data banks, data integration ...);

2) remote sensing, coastal zone management;

3) advanced graphics and visualization.

The candidate must have the citizenship of an EU Member State.

Probable starting date for the work: 1 October, 1997.

Interested candidates should send their CV by e-mail or FAX
within the next ten days to:
----------------------------------------------------------------------
|  Dr. Ing. Wolfram Schrimpf    European Commission                  |
|                               Joint Research Centre                |
|                               Space Applications Institute         |
|                               T.P. 690                             |
|                               I-21020 Ispra (VA)                   |
|                               ITALY                                |
|                                                                    |
|                               Tel. +39.332.78.5352/9177            |
|                               FAX. +39.332.789648                  |
|                               e-mail: wolfram.schrimpf@...      |
----------------------------------------------------------------------
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CAVE CONSERVANCY FOUNDATION
     GRADUATE FELLOWSHIP IN KARST STUDIES

The Cave Conservancy Foundation is sponsoring an annual competition for
a $15,000 graduate fellowship in karst studies.  The fellowship,
designed to foster graduate research, will be awarded to a master's or
doctoral student who is working on a thesis or dissertation in some
aspect of karst.  The work can be in any of the sciences or other
disciplines that  in someway has a relationship with karst terrain,
karst processes, caves, etc.  Competition will not be limited to the
classic sciences such as archeology, biology, geology and hydrology but
may include ecology, conservation, civil engineering, pollution,
restoration, water quality and other social issues resulting from karst
processes.   An applicant must be full-time graduate student at a U.S.
college or university.  Applications must include a thesis proposal,
graduate transcripts, and two letters of recommendation, one being from
the thesis advisor.  Applications are due by June 1.  Awards will be
announced by July 15.  For more information contact:

               		 Dr David Culver
		 Department of Biology
		 American University
		 Washington, DC 20016
or via E-mail <dculver@...>

Mail applications to:

		 Cave Conservancy Foundation
		 Attn. Graduate Fellowship Program
		 5300 W Marshall Street
		 Richmond, VA 28230

Note:  Please reply only to the addresses above, not the lists or me.

Thank you
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Hi,

I'll appreciate your advice. I am tring to do analysis of some data. I was not
succesful
with GEOEAS (I could not compiled). Splus is not working. I do not know if
600 points are a large array for SPlus but I got "bus error".
Can you suggest me other friendly free software. ( I already read the FAQ but
I'll appreciate
your opinions).
Thanks,
Octavio
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Here is a question for fractal experts !

I was wondering if any body would know the difference between the
fractal dimension and the fractal co-dimension (Is there a
fundamental difference between them ?)

Thank you for taking part of this discussion

Sincerely yours

Johan Perret
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At 09:48 AM 4/19/97 -0400, you wrote:
>Hi,
>
>I'll appreciate your advice. I am tring to do analysis of some data. I was
not succesful
>with GEOEAS (I could not compiled). Splus is not working. I do not know if
>600 points are a large array for SPlus but I got "bus error".
>Can you suggest me other friendly free software. ( I already read the FAQ
but I'll appreciate
>your opinions).
>Thanks,
>Octavio
>--

Give Phillip Ingram's page at http://atlas.es.mq.edu.au/users/pingram/sware.htm
a try.  I've had some success with his KSTAT and other programs for the DOS
environment.  He has a lot of additional links on his pages there.


Sincerely

Ed Houser
geoed1@...
"The young geologist looks at the Rocks"
"The experienced geologist talks to the Rocks"
"The old geologist simply listens to the Rocks"

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Dear all.

Sorry it have took long time to post the summary
concerning my question.

The first question,

>
> We read some books on geostatistics.
>
> In application to actual data in most books,
> it is not shown that why the semivariograms appeared in the analysis
> are selected.
>
> Does anyone have reference or comments ?
>

We have found following three criteria in some papers.

	 1. goodness of fit in variogram model fitting.
	 2. cross validation in kriging.

	 3. Akaike's Information Criterion with MLE.

In our analysis, criterion 1 has selected Gaussian model.
But the kriging surface with the fitted Gaussian model
has very strange feature.


The next question,

> I have one more question.
> If we assume a process is Gaussian,
> maximum likelihood (ML) estimator or
> restricted maximum likelihood (REML) estimator can be made
> for estimation of its covariance structure.
>
> I want to know another distributional assumptions on
> stochastic process which are often used in practice.

In analysis with density of metal or something,
many data behave like log normal distribution.
So, in this case, the data are to be log transformed.

Another transformation for non-normal data is
to disjunctive kriging.


Thank you those who have responsed my question.



Sincerely,

                   Jun Takeda
                   e-mail address:take@...
                   Dept. Math. Sci, Fac. Eng. Sci,
                   Osaka Univ., Toyonaka, Osaka 560, JAPAN
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Octavio,
Unless I missed an earlier posting, could you please tell me what you
are really trying to do.
thanks..
ALaa

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April 17, 1997

Dear Colleagues:

During the 16th World Congress of the ISSS scheduled for 20-26 August 1998
in Montpellier, France, a special symposia No. 17 " Advances in soil survey
using modern tools ; methods ands results " will be convened.

Contributed papers will be welcomed.  Please refer to the program and
registration brochure for detailed information about the format, dates, and
registration.  Should you need a copy, please send by E-mail to
isss@....   See also the Web server of the congress :
http://www.cirad.fr/isss.html"

Remember that deadline for oral presentations is April 30, 1997 - Poster
presentation can be submitted until August 30, 1997.

____________________________________________________________________________
_________
Commission V - Soil Genesis, classification and cartography
SYMPOSIUM NO. 17 : Advances in soil survey using modern tools ; methods
ands results

Convenor :
Mary E. Collins
Soil and Water Science Dept
University of Florida 2169 Mc Carty Hall
Gainesville FL 32611
USA
Email : mec@...

Co-Convenor
C.WALTER
Laboratoire de Science du Sol
ENSA/INRA
65 rue de St Brieuc
35042 Rennes
Email : cwalter@...

____________________________________________________________________________
__________
The following are goals of the symposium :

Advances in soil survey using modern tools:  methods and results


	 This symposium is intended for researchers with some background or
knowledge of the information available in the soil survey program, and who
have an interest in increasing their knowledge of the application of the
soil survey data.   The symposium seeks to explore a rapidly developing
field in which new tools have been developed to better study and use soil
survey data while observing soils in the field, characterizing soil
landscapes, determining and analyzing soil variability, and developing
models to characterize the spatial variability of soils. The objective of
the symposium is to present how modern tools or the application of new
theoretical approaches contribute to a refined spatial analysis and
knowledge of soil variability. »

	 New tools of soil characterization are first considered. Conventional
methods of observing soils have generally been slow and tedious, and often
result in a limited number of observations over a small area.   Individuals
are requiring more accurate and site-specific data on soil properties and
variability of soils at greater depths than previously attained in soil
surveys.  To fulfill the need for deeper and more intense sampling, precise
methods of observing soils are required.

Participants will learn about new developments in geophysical methods that
are helping to increase the application of tools such as the
ground-penetrating radar, magnetometers, electrical conductivity equipment,
infrared detectors, and other remote sensing techniques.  New laboratory
equipment as well field equipment will be discussed.   Systematic sampling
using geophysical methods and computer graphic techniques can enhance and
develop a better understanding of soils and the landscapes on which the
soils occur.   Problems related to the lack of quality soil data and the
limited quantity of data related to the application of soil surveys in
Geographic Information Systems (GIS) will be explored and evaluated.. The
ability to use new tools and technologies can result in rapid, reliable
interpretation of soils data on site.

	 The interest for soil spatial analysis of an evolutive theoretical
background  in such areas as artificial intelligence, geostatistics, fuzzy
logic, and mathematic modeling will be presented. The interest of coupling
soil observations with topographic parameters derived from Digital
Elevation Models will also be considered for soil spatial variability
modeling.

Modeling data from the theoretical background can be very useful in helping
to understand field data, and in helping to solve field problems.  This
symposium will stress the need to use and interpret quality field data and
illustrate the features and limitations of modeling the field data.




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Christian .WALTER
ENSA-INRA, Laboratoire de Science du Sol, 65 rue de Saint-Brieuc
35042 Rennes -
tél : 02-99-28-54-39 ou 02-99-28-54-22 (standard)
Fax : 02-99-28-54-30
E-mail : cwalter@...
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Hello

I am a geohydrologist with the Department of Water Affairs & Forestry
in South Africa.  We are busy with a regional scale project to improve
success rates when siting boreholes for rural groundwater supply and
have mapped geological lineaments from various remotely sensed
sources.  We have also gathered detailed borehole information (yield etc)
in the area.  I wish to statistically analyse this data on Arc/Info.

My specific geostatistical problem and therefore question is - what is the
appropriate statistical technique(s) to investigate the correlation between
the point source data (i.e. borehole yield) and the polygon/areal data
(lineament
density).  I would hope to see a significant positive correlation between
zones of high lineament density and above average borehole yield and
visa versa.

Any suggestions or comments would be most welcome.

Best Wishes



Alan Woodford
Specialist Scientist
Directorate:Geohydrology
Department Water Affairs & Forestry
P/Bag X16
Sanlamhof
7532
SOUTH AFRICA

Phone Number    : (+27) (21) 950 7100
Fax Number      : (+27) (21) 946 3666
E-Mail Address  : ogb@...
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Dear all,

I have three questions, as follows (supposed I have non-evenly
distributed point data)

1) is that true that stationarity of data is just a question of
scale?

If  I make a search window too small, a mean of the data in this
window will be very different from global mean , so I have
non-stationarity.

If I make a search window large enough, a mean of the data in the
window will be close to the global mean, so I have stationarity.

Usually stationarity will be also checked through the form of
variogramm. Variogramms without sill are said to be from
non-stationary random process. Typical such are power variograms,
including a linear one. But if I take into account, that spherical
and exponential variograms are linear and gaussian model is parabolic
NEAR THE ORIGIN, it looks to me, as  such variograms were just a part
of transition variograms (with a sill) near origin, so my region is
just not large enough to show stationarity of data. So should one use
exponential and gaussian variograms with a large range (larger as
size of the region) to fit experimental variogram without sill?

2) the next question is about modelling an anisotropy for kriging. If
I have very different  variograms in different directions, I can
transform coordinates and calculate equivalent models with reduced
distances to deal with it.

The question is: why just not use different theoretical variograms for
different directions. If one builds an ordinary kriging system, one
could just pick up different variograms depending on the angle
between i-th  and j-th point?

3) and the last question: should one use all data points for kriging
or restrict to the nearby of them? Isaaks&Srivastava vote for the
neighbourhood searching, and Peter Kitanidis in "Introduction to
Geostatistics" write:
Another motivation has been the estimate at x0 dependent only on
observations in its neighbourhoods, which is often a desirable
characteristic. However, the same objective can be achieved by using
all data with an appropriate variogram(such as the linear one) that
assigns vary small weights to observations at distant points. If the
weights corresponding to points near the border of the neighbourhood
are not small and the moving neighborhood method is applied in
contouring, the estimated surface will have discontinuities that are
unsightly as well as unreasonable, if they are the artifact of the
arbitrarily selection of a moving neighbourhood.

So - moving neighbourhood - is it good or bad ( beside of the question of
computational effectiveness)?

Thanx,
Konstantin.

Konstantin Malakhanov, wiss. Mitarbeiter/research engineer

IWW, RWTH Aachen
Tel. 0241-807343
Fax. 0241-8888348
E-Mail: kosta@...
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Stationarity is a property of the random function, not the
data. If one computes a mean on a set of (spatial) data then
you are computing a spatial average not an ensemble average.
Stationarity pertains to the invariance of the ensemble
mean.

Unfortunately there is no way to compute the ensemble mean
because there are no replications.

See my article in Math Geology, circa 1988.

However there are characteristics that would suggest
non-stationarity such as the quadratic or higher growth
rate of the sample variogram. Plotting data values
against a position coordinate may identify a possible
non-stationarity.

Note that there are several forms of stationarity of
a random function, strong (which depends on the translation
invariance of joint distributions and this form is not
usually used in geostatistics), second order which depends
not only on the mean being constant but also the covariance
being a function of the separation vector, finally there
is intrinsic which relates to the variogram (this is weaker
than second order). If one is working with IRF-k's then
there are even weaker forms of stationarity.

Stationarity is not testable, i.e., a statistical test, because
the test would require stationarity and would require having
data for more than one realization of the random function.

With respect to the idea of using different variogram models
for different directions, that would in general violate the
requirement of having a valid model. The conditional
negative definiteness condition is necessary (and sufficient)
to ensure that the estimation variance is non-negative
and that the kriging system has a unique solution. That is
not to say that there might not be some combinations of
variograms in this manner that are valid but it is very
hard to prove. See Myers and Journel, Math. Geology
circa 1990 for examples of how this fails in even a very
simple case.

Donald E. Myers
Department of Mathematics
University of Arizona
Tucson, AZ
myers@...
http://www.u.arizona.edu/~donaldm
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Greetings,

there are few changes in SIC 97:


1)  Initially limited to 40 participants, there is now no restriction anymore.
However, the Editorial
Committee will have to select the papers which will be printed in the
proceedings because of publishing
constraints. The current idea  would be to have the selected papers fully
presented in the proceedings,
the other contributions will  have only their results and a brief description of
the methods presented
in an annexe. The number of papers which will be selected for the proceedings
has not been defined yet.

Participants can of course resign/join at any time (please contact me in any of
these cases).

2) Initally planned for September 97, it will start much earlier than expected.
This for technical reasons.
The Editorial Committee is currently selecting the data and defining the
deadlines.
Data will be released during the month of May and results will have to be sent
to the reviewers around
September.


3) SIC 97 will be published in proceedings format. There is also a big chance to
have the best papers
reselected again and published in an international Journal. We will tell more
about it when a decision
will be taken.


Best regards,

Gregoire


<gregoire.dubois@...>
<Moderator of the ai-geostats mailing list>
<http://java.ei.jrc.it/rem/gregoire/>
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Hi,

I'm fairly new to spatial statistics and have come across a problem.  I'm
using semi-variograms as a descriptive tool to quantify spatial
heterogeneity in nutrient concentrations in stream water.  I'm primarily
interested in fitting a theoretical variogram to my experimental data to
obtain a range, which I interpret as patch size, and can then compare to
patch sizes for other nutrients or for the same nutrient at different
times of the year.  My initial data are all one-dimensional transects
(since streams flow in one direction), with samples every 25 m over a
total of 10 km.
My problem is this: in some of the experimental variograms, it looks to
me as if the variance increases to a sill, remains at that sill for
several lags, and then increases again to a second sill.  Since I am
interested in finding the range, I would like to fit a model with two
ranges. I have been using GSplus, which does not have any models with
multiple ranges.  I also tried using a double spherical model, which I
found in the literature, but it does not really level off at the first
sill the way my experimental variograms do.  The only solution I can
think of is to first fit a spherical model to an empirical variogram
calculated using one maximum lag (the lag where the variogram begins to
increase for the second time), getting one range, and then fit an
empirical variogram calculated using a larger maximum lag, to get the
second range.  Is this legitimate?  Is there any objective way to
determine what the maximum lags should be?

Any advice is appreciated.  As well as GSplus, I have also been using
Splus spatial stats.

Thanks,
Lisa

***************************************************************************
* Lisa Dent                			 lisa.dent@... *
* Department of Zoology 	  		 (602) 965-6478   *
* Arizona State University 						  *
* Tempe, AZ 85287-1501 						  *
* 		        						  *
***************************************************************************


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Dear all,
         someone could tell me what is the expression for the
         cokriging variance in the case of simple cokriging.
         I have reading the usual references and I don't manage
         find this expresion.

         Thanks in advance.
Francisco Abarca  fabarca@...
Dpto. Geodinámica  http://carpanta.ugr.es/~fabarca
Facultad de Ciencias  Tfno/Fax: + 034 58 243363
Universidad de Granada

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