[GRASS-user] using grass on rasters without converting?

[Glynn Clements]

Markus Neteler wrote:

> >> r.external - Link GDAL supported raster file to a binary raster map layer.
> >> http://grass.osgeo.org/grass64/manuals/html64_user/r.external.html
> >>
> >
> > This solves a need for me too. Could something like that be done for WMS
> > services, i.e. not downloading them with r.in.wms, but linking them without
> > making a local copy?
> 
> In theory, r.external might also accept WMS since GDAL does it:
> http://www.gdal.org/frmt_wms.html

> # this gets stuck:
> d.rast gdal_wms
>    0%
> 
> strace shows
> ...
> select(8, [6 7], [], [], {0, 100000})   = 0 (Timeout)
> poll([{fd=6, events=POLLIN|POLLPRI}], 1, 0) = 0
> poll([{fd=7, events=POLLIN|POLLPRI}], 1, 0) = 0
> select(8, [6 7], [], [], {0, 100000})   = 0 (Timeout)
> ...
> 
> Maybe some update magic is needed internally (but maybe
> I am exaggerating right now...).

Maybe GDAL can't handle skipping rows for WMS? Due to the region
mapping, GRASS typically doesn't request rows sequentially (it may
skip rows, or request them in an arbitrary order, even reverse order).

-- 
Glynn Clements <glynn at gclements.plus.com>