[GRASS-user] raster boundings

GRASS GRASS user
1

Dear GRASS user,

how can I obtain the boundings of raster subpart like the minimum rectangle
around a certain category. I need it to specify the region for a
computationally intensive operation on a small part of the entire raster. The
problem I have is the mapcalc step to operate with huge raster datasets
containing "novalue" data mainly together with only small categorized areas.
Defining a mask a
mask for the relevant value doesnt work - the mapcalc takes the same long(!)
time as without a mask. So specifying region is the next idea.

Thanks a lot for some solution...

Regards,
Christian.

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2

Just an idea:
1) Create new map with r.reclass where MyCat=1 OtherData=NULL and
2) then use g.region zoom=myreclassmap

Hope this helps,
Maris.

2008/5/6, Christian Schwartze <Christian.Schwartze@uni-jena.de>:

Dear GRASS user,

how can I obtain the boundings of raster subpart like the minimum rectangle
around a certain category. I need it to specify the region for a
computationally intensive operation on a small part of the entire raster.
The
problem I have is the mapcalc step to operate with huge raster datasets
containing "novalue" data mainly together with only small categorized areas.
Defining a mask a
mask for the relevant value doesnt work - the mapcalc takes the same long(!)
time as without a mask. So specifying region is the next idea.

Thanks a lot for some solution...

Regards,
Christian.

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3

Thanks - it works! So better reading the help pages... :wink: But
unfortunately a little bit to slow when applying on large raster...

Best regards,
Christian.

Am Dienstag, den 06.05.2008, 17:28 +0300 schrieb Maris Nartiss:

Just an idea:
1) Create new map with r.reclass where MyCat=1 OtherData=NULL and
2) then use g.region zoom=myreclassmap

Hope this helps,
Maris.

2008/5/6, Christian Schwartze <Christian.Schwartze@uni-jena.de>:
> Dear GRASS user,
>
> how can I obtain the boundings of raster subpart like the minimum rectangle
> around a certain category. I need it to specify the region for a
> computationally intensive operation on a small part of the entire raster.
> The
> problem I have is the mapcalc step to operate with huge raster datasets
> containing "novalue" data mainly together with only small categorized areas.
> Defining a mask a
> mask for the relevant value doesnt work - the mapcalc takes the same long(!)
> time as without a mask. So specifying region is the next idea.
>
> Thanks a lot for some solution...
>
> Regards,
> Christian.
>
>
>
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> This mail was sent through http://webmail.uni-jena.de
> _______________________________________________
> grass-user mailing list
> grass-user@lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/grass-user
>