- View SourceHi all list members

Suppose that g denote the semi-variogram and C

denote the Covariogram functions. According to

Cressie(1993, P. 67) the relation is

g(h) = C(0) - C(h)

where h is the distance vector.In the isotropic case

C(0) = total sill = c0 + c

I have an Anisotropic Variogram in which c is varying

with direction.Therefore my question is what is C(0)

in this case?

=====

__________________________________________________

Do You Yahoo!?

LAUNCH - Your Yahoo! Music Experience

http://launch.yahoo.com

--

* To post a message to the list, send it to ai-geostats@...

* 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 majordomo@... 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 - View SourceHi Dear doctor Abedini

I have constructed a more general variogram model, in

which all of the parameters are varying with

direction. My model more general than range anisotropy

and sill anisotropy. Since I want to simulate from

this model ,with cholesky decomposition method, I need

the covariogram model, which is respected to my

variogram model. Therefore I need the relation between

variogram and covariogram. In fact I need to specify

C(0).

Thank you: W.

--- "Dr. M.J. Abedini from Civil Eng."

<abedini@...> wrote:>

__________________________________________________

>

> Mr. Webster

>

> First of all, C in that equation is covariance which

> is totally different

> from covariogram.

>

> As for c(0), first you need to specify which type of

> anisotropy you have.

> In geometric anisotropy, range is direction

> dependent and sill [c(0)] is

> constant while in zonal anisotropy, the sill is

> direction dependent and

> range is constant. You might have a combination of

> geometric and zonal

> anisotropy for which both sill and range are

> direction dependent. You may

> even have nugget effect anisotropy for which negget

> is direction

> dependent.

>

> I will create a list of papers on modeling

> anisotropy and will forward it

> to you shortly.

>

> Thanks

> Abedini

>

> On Mon, 13 May 2002, jack webster wrote:

>

> > Hi all list members

> > Suppose that g denote the semi-variogram and C

> > denote the Covariogram functions. According to

> > Cressie(1993, P. 67) the relation is

> > g(h) = C(0) - C(h)

> > where h is the distance vector.In the isotropic

> case

> > C(0) = total sill = c0 +

> c

> > I have an Anisotropic Variogram in which c is

> varying

> > with direction.Therefore my question is what is

> C(0)

> > in this case?

> >

> > =====

> >

> >

> > __________________________________________________

> > Do You Yahoo!?

> > LAUNCH - Your Yahoo! Music Experience

> > http://launch.yahoo.com

> >

> > --

> > * To post a message to the list, send it to

> ai-geostats@...

> > * 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

> majordomo@... 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

> >

>

Do You Yahoo!?

LAUNCH - Your Yahoo! Music Experience

http://launch.yahoo.com

--

* To post a message to the list, send it to ai-geostats@...

* 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 majordomo@... 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 - View SourceDear Jack Webster,

The mapping of the variogram to the covariogram is not one to one.

When c(h) is a covariogram having g(h) as variogram, then c(h)+k for any

positive real number k has the same variogram. Thus for your simulations it is appropriate to

use c(h)=k-g(h) for any k larger than (or equal to) the maximum (or supreme)

of your directional sills.

Best regards

Gerald v.d. Boogaart

jack webster wrote:>

--

> Hi Dear doctor Abedini

> I have constructed a more general variogram model, in

> which all of the parameters are varying with

> direction. My model more general than range anisotropy

> and sill anisotropy. Since I want to simulate from

> this model ,with cholesky decomposition method, I need

> the covariogram model, which is respected to my

> variogram model. Therefore I need the relation between

> variogram and covariogram. In fact I need to specify

> C(0).

* To post a message to the list, send it to ai-geostats@...

* 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 majordomo@... 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 - View SourceHi Dear doctor Myers

Thank you for replying

I have constructed a more general variogram model, in

which all of the parameters are varying with

direction. My model more general than range anisotropy

and sill anisotropy. Since I want to simulate from

this model ,with cholesky decomposition method, I need

the covariogram model, which is respected to my

variogram model. Therefore I need the relation between

variogram and covariogram. In fact I need to specify

C(0) in term of the parameters of my model ( My model

has 6 parameters c01,c02( Nuggets) ,c1,c2 (partial

sill) and a1,a2 (Ranges) ), because when it be known

C(h) = C(0) - g(h)

Thank you again: Webster

--- "Donald E. Myers" <myers@...> wrote:> Two observations

__________________________________________________

>

> 1. The relationship between the variogram and the

> covariance function is

> only valid in the case of second order stationarity

> (presumably you are

> making the assumption of second order stationarity)

>

> 2. You said you had an "Anisotropic variogram", do

> you mean you have a

> model for a variogram with anisotropy or do you mean

> that the

> directional sample variograms indicate a change in

> the sill with

> direction? The apparent sill indicated by a sample

> variogram

> (directional or not) will combine the nugget effect

> component and also

> the sill due to the non-nugget part of the variogram

> model, in addition

> the nugget effect component will be separately

> evident on the graph of

> the sample variogram. If you check the various

> geostatistical software

> packages you will see that they only allow for a

> geometric anisotropy in

> the variogram model, this means that the RANGE of

> the variogram changes

> with respect to direction, the software does not

> allow the sill to

> change with respect to direction. To allow the sill

> to change you would

> need a "zonal" aniostropy, i.e., a non-geometric

> anisotropy and the

> problem is constructing a valid variogram model with

> this kind of

> anisotropy.

>

> A. Journel and I showed that one method that had

> been used leads to

> semi-definite models, i.e., non-invertible

> coefficient matrices for the

> * kriging system 1990, D .E. Myers and A. Journel,

> Variograms with Zonal

> Anisotropies and Non-Invertible Kriging Systems.

> Math. Geology 22, 779-785

>

>

>

> Donald E. Myers

> http://www.u.arizona.edu/~donaldm

>

> jack webster wrote:

>

> >Hi all list members

> >Suppose that g denote the semi-variogram and C

> >denote the Covariogram functions. According to

> >Cressie(1993, P. 67) the relation is

> > g(h) = C(0) - C(h)

> >where h is the distance vector.In the isotropic

> case

> > C(0) = total sill = c0 +

> c

> >I have an Anisotropic Variogram in which c is

> varying

> >with direction.Therefore my question is what is

> C(0)

> >in this case?

> >

> >=====

> >

> >

> >__________________________________________________

> >Do You Yahoo!?

> >LAUNCH - Your Yahoo! Music Experience

> >http://launch.yahoo.com

> >

> >--

> >* To post a message to the list, send it to

> ai-geostats@...

> >* 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

> majordomo@... 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

> >

> >

>

>

Do You Yahoo!?

LAUNCH - Your Yahoo! Music Experience

http://launch.yahoo.com

--

* To post a message to the list, send it to ai-geostats@...

* 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 majordomo@... 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