[GRASS-user] interpolate raster map

[Rainer M Krug]

On Thu, May 22, 2008 at 2:17 PM, Hamish <hamish_b at yahoo.com> wrote:
> [ah, it dumped the server-error email in my draft folder. here it is]
>
>
> Rainer Krug:
>> I have two raster maps, one (mapA) based on a raster map of
>> a much lower resolution (see attached picture) and the other
>> one is in the MASK (pink). I would like to do two things:
>>
>> 1) "smooth" mapA, so that it is not as grainy as
>> it is now. I know that that will introduce error,
>> but the error will be less important then the edges
>> based on the coarser resolution.
>
> set resolution to that of the MASK and use r.resamp.interp or r.resamp.rst.
> then reapply the MASK with r.mapcalc "croped=interped"

Thanks for the answer - I am in the process of trying it out. But:
When I try to use r.resamp.rst, I get the error message "Input map
resolution differs from current region resolution!". I thought that
r.resamp.rst is doing exactly that - changing the resolution?

>
>> 2) extrapolate to the areas not covered by mapA, but part
>> of MASK. again - I am aware that this will introduce considerable
>> error, but the same applies as in the previous case. So what I would
>> like to do here, is essentially fill the edges with the values of the
>> adjacend cells which have values.
>
> r.grow for that, but r.resamp.rst may do a nice job around the edges and maybe it is good enough to keep.
>
>
>> I looked at resampling (for (1)), but it increases the edge
>> without data, which is not acceptable for me.
>
> which method?
> you could always use the original low res map as a mask.
>
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> Hamish
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-- 
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation
Biology, UCT), Dipl. Phys. (Germany)

Plant Conservation Unit
Department of Botany
University of Cape Town
Rondebosch 7701
South Africa