[GRASS-user] r.tile behaviour

[Sajid Pareeth]

Thank you both,

I got confused between first and last row tiles and the middle ones.
The overlap is fine on first and last row tiles.

Regards

Sajid

On Wed, Nov 7, 2018 at 7:37 PM Markus Metz <markus.metz.giswork at gmail.com>
wrote:

>
>
> On Wed, Nov 7, 2018 at 7:06 PM Veronica Andreo <veroandreo at gmail.com>
> wrote:
> >
> > Hi Sajid,
> >
> > I have never used r.tile before, but checking the code [1], it
> multiplies the overlap by 2, so there's why. Now guesstimating, if I set an
> overlap of 50, I would expect to have that overlap on both sides of the
> desired size of the tiles, so maybe that's why it is doubled ?
>
> In princliple that's correct, but not for the first and last row and
> column of tiles.
>
> In Sajid's example, the first and last row of tiles should have 725 rows
> (675 + 50) and all other tiles 775 rows (675 + 2 * 50). Accordingly for
> columns.
>
> That should be relatively easy to fix.
>
> Markus M
> >
> > HTH,
> > Vero
> >
> > [1]
> https://trac.osgeo.org/grass/browser/grass/trunk/raster/r.tile/main.c#L101
> >
> > El mié., 7 nov. 2018 a las 15:08, Sajid Pareeth (<spareeth at gmail.com>)
> escribió:
> >>
> >> Hi all
> >>
> >> The r.tile module don't have overwrite flag, so if we re run the module
> with different parameters but with same output prefix name, then it will
> rewrite output with out warning.
> >> Is this intentional?
> >>
> >> Another point is, if I use overlap option it adds double the overlap
> cells to the output maps.
> >>
> >> For example in the NC location:
> >>>
> >>> r.info elevation -g
> >>
> >> rows=1350
> >> cols=1500
> >>
> >>> r.tile input=elevation output=elev_tile width=750 height=675
> >>> r.info elev_tile-001-001 -g
> >>
> >> rows=675
> >> cols=750
> >>
> >>> r.tile input=elevation output=elev_tile width=750 height=675 overlap=50
> >>> r.info elev_tile-001-001 -g
> >>
> >> rows=775 (+ 100)
> >> cols=850 (+ 100)
> >>
> >> In the last case the rows and cols should be 725 and 800 respectively,
> as it should add 50 cells as overlap to each tile? Or am I missing
> something?
> >>
> >> Regards
> >>
> >> Sajid
> >>
> >>
> >>
> >>
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