[R-sig-Geo] block and output grid size in block kriging

[Edzer Pebesma]

The drawing (thanks!) suggests that you think that the point over which
a kriging block is centered is not the center point of a grid cell. This
is wrong: the coordinates of grid cells, obtained e.g. by

require(sp)
demo(meuse, ask = FALSE)
coordinates(meuse.grid)

are grid cell centers. You can verify this, e.g. for the first 20 grid
cells / pixels with

plot(as(meuse.grid[1:20,], "SpatialPolygons"))
points(meuse.grid[1:20,])

I also tried to point out in my previous answer that you are not looking
at "ordinary kriging" vs "block kriging", but at "ordinary point
kriging" vs. "ordinary block kriging". If your observations are not
constant and you don't use a pure nugget model, point kriging and block
kriging estimates will always be different.


On 02/12/2015 05:22 PM, subash wrote:
> Dear Edzer,
> 
> Thanks for the clarification.Still it not clear to me.
> 
> I added an image below showing the block and the grids. If my visualization
> is correct then for a block of (40,40), there is only 1 grid points. If Yes,
> then ordinary kriging estimate and block kriging estimate for block size
> (40,40) should be same.
> 
> <http://r-sig-geo.2731867.n2.nabble.com/file/n7587782/block_kriging_framework.png> 
> 
> Thanks in advance
> 
> 
> 
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> 
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-- 
Edzer Pebesma
Institute for Geoinformatics, University of Münster,
Heisenbergstraße 2, 48149 Münster, Germany; +49 251 83 33081
Journal of Statistical Software:   http://www.jstatsoft.org/
Computers & Geosciences: http://elsevier.com/locate/inca/398

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