[GRASS-user] calculating perimeter per patch

[Markus Metz]

On Sat, Feb 12, 2011 at 11:58 AM, Milton Cezar Ribeiro
<miltinho.astronauta at gmail.com> wrote:
> Hi Markus,
>
> Thanks for the reply. In fact a vector-based should solve this.
> But, unfortulatelly, as I am working with a very large raster map
> (48,000 x 60,000 pixels; 250,000 clumps), and GRASS fail when
> I try r.to.vect under Windows/Vista. Is there any other options
> of convert large raster maps to vector, instead of r.to.vect?
>
No, but you could try a recent version of GRASS 7 and after starting
GRASS, set at the commandline

export GRASS_VECTOR_LOWMEM=1

then try r.to.vect

It will take some time, but it should finish eventually.

Markus M

>
> Markus Metz:
>>
>> Milton Cezar Ribeiro:
>> > Dear all,
>> >
>> > I have a raster map where each patch (i.e. forest fragment) have
>> > different
>> > ID.
>> > I need to estimate the perimeter per patch, but R.le.patch can't do the
>> > job.
>>
>> Have you tried a vector approach? Then the perimeter can be simply
>> uploaded with
>> v.to.db option=perimeter.
>>
>> (Watch out for the fractal problem, both r.le.patch and v.to.db)
>>
>> Markus M
>>
>> > ------------
>> > GRASS 6.4> r.le.patch map=fragments sam=w per=p1 siz=s1 out=STATS.txt
>> >
>> > PARAMETER CHOICES:
>> >         MAP:      fragments
>> >         SAMPLE:   whole map     TRACING:  8 neighbor
>> >         SIZE MEASURES:
>> >                   mean patch size
>> >         PERIMETER MEASURES:
>> >                   sum of perims
>> >
>> > R.LE.PATCH IS WORKING....;
>> >
>> > ERROR: G_calloc: unable to allocate 24806 * 8 bytes at alloc_cell.c:83
>> > ------------
>> >
>> > Any hint?
>> >
>> > bests
>> >
>> > milton
>> >
>> > _______________________________________________
>> > grass-user mailing list
>> > grass-user at lists.osgeo.org
>> > http://lists.osgeo.org/mailman/listinfo/grass-user
>> >
>> >
>
>