[GRASS-user] eliminate isolated pixel groups - solved
Florian Kindl
florian.kindl at uibk.ac.at
Thu Jan 18 15:05:05 EST 2007
Glynn,
thank you very much for your first-class help!
I made a good step forward with your advice.
I just wonder how you count 20 in step 3, though ;)
Thanks,
Florian
On Jan 17 [19:55], Glynn Clements wrote:
>
> My first attempt would be:
>
> 1. r.mapcalc "${RI}.null = isnull(${RI})"
>
> 2. r.mfilter input=${RI}.null ouput=${RI}.count filter=ring5x5
>
> where ring5x5 is:
>
> TITLE 5x5 sum
> MATRIX 5
> 1 1 1 1 1
> 1 0 0 0 1
> 1 0 0 0 1
> 1 0 0 0 1
> 1 1 1 1 1
> DIVISOR 1
> TYPE P
>
> 3. r.mapcalc "${RI}.ring = ${RI}.count == 20"
r.mapcalc "${RI}.ring = ${RI}.count == 16"
>
> 4. r.mfilter input=${RI}.ring ouput=${RI}.change filter=box3x3
>
> where box3x3 is:
>
> TITLE 3x3 sum
> MATRIX 3
> 1 1 1
> 1 1 1
> 1 1 1
> DIVISOR 1
> TYPE P
>
> 5. r.mapcalc "${RO} = if(${RI}.change,null(),${RI})"
>
> 6. g.remove rast=${RI}.null,${RI}.count,${RI}.ring,${RI}.change
>
> While you could use r.mapcalc instead of r.mfilter for steps 2 and 4,
> the r.mfilter approach scales more readily to larger windows.
>
> --
> Glynn Clements <glynn at gclements.plus.com>
>
--
Florian Kindl
Institute of Geography
University of Innsbruck
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