[R-sig-Geo] UK, KED or OCK? [SEC=UNCLASSIFIED]

[Edzer Pebesma]

Hi Jin,

Which differences do you exactly refer to? I'd say that what happens in 
demo(cokriging) is ordinary cokriging. As it says:
...
[using ordinary cokriging]

Best regards,
--
Edzer

Jin.Li at ga.gov.au wrote:
> Hi All,
>
>  
>
> I am going to compare a few spatial interpolation techniques including
> kriging with an external drift (KED) and ordinary co-kriging (OCK) (such as
> those defined in: Goovaerts, 1997. Geostatistics for Natural Resources
> Evaluation.) to interpolate marine sediment data (mud content in this case)
> using bathymetry as a secondary variable. However, it seems that the ordinary
> cokriging in gstat as shown in demo(cokriging) is different from the OCK we
> planned to use. Is it possible to do such OCK in gstat? Any comments and
> example? Thanks.
>
>  
>
> As to KED, I tried 
>
>   
>> vgm1 <- variogram(sqrt(mud)~bathy, data.file.dev)
>>     
>
>   
>> model.1 <- fit.variogram(vgm1,vgm(1,"Sph",5,1))
>>     
>
>   
>> # plot(vgm1, model.1)
>>     
>
>   
>> coordinates(data.file.pred) = ~LON+LAT
>>     
>
>   
>> mud.ok <- krige(sqrt(mud)~bathy, data.file.dev, data.file.pred, model =
>>     
> model.1)
>
> [using universal kriging]
>
>  
>
>   
>> vgm1 <- variogram(sqrt(mud)~LON+LAT, data.file.dev)
>>     
>
>   
>> model.1 <- fit.variogram(vgm1,vgm(1,"Sph",5,1))
>>     
>
>   
>> # plot(vgm1, model.1)
>>     
>
>   
>> coordinates(data.file.pred) = ~LON+LAT
>>     
>
>   
>> mud.ok <- krige(sqrt(mud)~LON+LAT, data.file.dev, data.file.pred, model =
>>     
> model.1)
>
> [using universal kriging]
>
>  
>
> Both of them are UK. But the first one seems regression kriging. Is it
> identical to KED in this case? If not, any comments and examples of KED are
> appreciated.
>
>  
>
> Cheers,
>
>  
>
> Jin
>
> --------------------------------------------
>
> Jin Li, PhD
>
> Spatial Modeller/
>
> Computational Statistician
>
> Marine & Coastal Environment
>
> Geoscience Australia
>
>
>
> Ph: 61 (02) 6249 9899
>
> Fax: 61 (02) 6249 9956
>
> email: jin.li at ga.gov.au <mailto:jin.li at ga.gov.au> 
>
> --------------------------------------------
>
>
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>
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>   

-- 
Edzer Pebesma
Institute for Geoinformatics (ifgi), University of Münster,
Weseler Straße 253, 48151 Münster, Germany.  Phone: +49 251
8333081, Fax: +49 251 8339763  http://ifgi.uni-muenster.de/