[GRASS5] [bug #859] (grass) raster data at lower resolution: no resampling...

[Helena Mitasova]

"Eric G. Miller" wrote:

> As far as I can tell, in a nutshell:
>
> The code attempts to map the cell row/col value that is most closely
> aligned with the center of the region row/col.  It builds an explicit
> column mapping, and leaves the decision to which rows to use for
> each row fetch operation.

Markus, if I understand correctly what Eric writes here it appears
that when resampling to lower resolution, GRASS uses the value which
is in a high resolution cell located in the center (or close to the
center ) of the low resolution cell.
I think that this is the best thing it can do both for field and
category data when it
does not know what type of phenomenon the data represent.
I don't think that we have a problem here although some warning about
this behavior
would be appropriate and it definitely needs to be documented.

Helena

>
>
> It's difficult to follow a lot of that code since it uses globals
> and additionally uses #define's to rename various parts of a global
> data structure.  Relevant files include: G.h, opencell.c, get_row.c,
> window_map.c, and probably a few others (depending on what you think
> is relevant).
>
> All of the low-level byte encoding/compression at the file level is
> not relevant to the mapping of cell values to match the region.
>
> --
> Eric G. Miller <egm2 at jps.net>
> _______________________________________________
> grass5 mailing list
> grass5 at grass.itc.it
> http://grass.itc.it/mailman/listinfo/grass5