Hi. I am ecologist, too. While I am not a geostatistician, I don't recall
seeing strong arguments to suggest that some processes lead to one spatial
model rather than others. Of course, one might argue the other way
around--that some models might indicate more or less covariance at, say,
small separation distances. However, such an argument would likely--for
ecologists at least--be specious because, given the size of the datasets we
typically work with, such an argument would likely be based on impossibly
small sample sizes. of course, such an argument would also be using the
data to infer a hypothesis--a general no-no in traditional statistics. my
two cents. cheers, brian
****************************************************************
Brian Gray
USGS Upper Midwest Environmental Sciences Center
575 Lester Avenue, Onalaska, WI 54650
ph 608-783-7550 ext 19, FAX 608-783-8058
[EMAIL PROTECTED]
*****************************************************************
"nic-zac@liber
o.it" <nic-zac To: [EMAIL PROTECTED]
Sent by: cc:
ai-geostats-li Subject: AI-GEOSTATS: Basic structure
interpretation
[EMAIL PROTECTED]
03/06/2002
02:56 AM
Please respond
to
"nic-zac@liber
o.it"
I'm re-posting my question becouse i've experienced some problems with
my e-mail service.
It's a newby question so sorry for bothering.
After reading Goovaerts' Geostatistics for Natural Resources Evaluation
and Isaaks and Srivastava's Applied Geostatistics I still haven't found
a way to corectly choose among variogram models.
Is a spherical model linked closer to a particular type of spatial
process? Are continous and smooth processes better described by
sphercial or and exponential model? Choosing between a sphericl or an
exponetial model is just a matter of fitting to experimental variogram
or is there specific reason on how the process under analysis works?
As an ecologist I have to provide a "meaningful" explanation of why
using a specific kind of model to describe my experimental variogram of
an difference image of NDVI values derived from Landsat satellite.
Any suggestion will be helpful.
Thanks to all.
NiCoLa
***********************************************************************
*
* Dott. Nicola Zaccarelli
* Lab. di Ecologia del Paesaggio
* Dip. di Scienze e Tecnologie Biologiche ed Ambientali
* Universit� di Lecce
*
***********************************************************************
Prov.le Lecce-Monteroni
73100 - LECCE
Tel. (+39)- 0832-320.896
Fax: (+39)- 0832-320.626
e-mail: [EMAIL PROTECTED]
[EMAIL PROTECTED]
NiCoLa
___________________________________________
Dott. Nicola Zaccarelli
C.N.R.-I.I.A.
tel. 0832-320.886
tel. 0832-320.896
--
* To post a message to the list, send it to [EMAIL PROTECTED]
* As a general service to the users, please remember to post a summary of any useful
responses to your questions.
* To unsubscribe, send an email to [EMAIL PROTECTED] with no subject and "unsubscribe
ai-geostats" followed by "end" on the next line in the message body. DO NOT SEND
Subscribe/Unsubscribe requests to the list
* Support to the list is provided at http://www.ai-geostats.org
