## AI-GEOSTATS: vertical semivariogram with gstat

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• Dear list members, I’m using GSTAT to build a 3D semivariogram, I find three directional semivariograms: Direction nug
Message 1 of 2 , Jan 30, 2004
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Dear list members,

Im using GSTAT to build a 3D semivariogram,

I find three directional semivariograms:

Direction nug psill range

30 (in the plane) 0.25 0.19 805

120 (in the plane) 0.25 0.19 687

vertical 0.25 0.19 3.26

I introduce in GSTAT this command:

Sill range p q r s t

vgm(0.19,Gau, 805, 0.25, anis=c(30, 0, 0, 0.85, 0.004))

Where 0.85 = (687/805) and 0.004 = (3.26/805)

When I plot this model with the sperimental semivariograms in the direction 30 and 120 (in the plane), this model works well because it follow the sperimental semivariogram but if I plot this model with the vertical semivariogram, it is a line around the value 0.25 while I expected that it reaches the sill (0.19+ 0.25) at 3.26 m. I tried to change the angles q and r, but if the model is good for the vertical direction then it doesnt work with the other two directions (30 and 120).

The command to find the vertical variogram was:

> variogram(cadmiog, cuttoff=4, width=4/8,alpha=0, beta=90, tol.hor=90, tol.ver=15, cloud=FALSE).

I apologise for this question but Im at the beginning with GSTAT and Im doing something wrong but I cannot understand where.

Thank you very much for your attention,

Best regards

Lisa

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• ... I don t have your data, but think I can more or less reproduce your results. Directional variograms only plot (at least, the should plot) right, currently,
Message 2 of 2 , Feb 4, 2004
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lisa pizzol wrote:

> Dear list members,
>
>
>
> I'm using GSTAT to build a 3D semivariogram,
>
> I find three directional semivariograms:
>
...

> The command to find the vertical variogram was:
>
> > variogram(cadmiog, cuttoff=4, width=4/8,alpha=0, beta=90,
> tol.hor=90, tol.ver=15, cloud=FALSE).
>
> I apologise for this question but I'm at the beginning with GSTAT and
> I'm doing something wrong but I cannot understand where.
>
>
>
I don't have your data, but think I can more or less reproduce your results.
Directional variograms only plot (at least, the should plot) right,
currently, when
you pass a set of directions to the variogram command, and not when you pass
a single direction. I will look into the issue, it is clearly a bug.
--
Edzer

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