[GRASS-user] CHELSA climate data set

[Markus Metz]

On Fri, Feb 10, 2017 at 5:53 PM, Paulo van Breugel <p.vanbreugel at gmail.com>
wrote:
>
>
>
> On 10-02-17 17:15, Markus Metz wrote:
>
>
>
> On Tue, Feb 7, 2017 at 3:43 PM, Markus Neteler <neteler at osgeo.org> wrote:
> >
> > On Tue, Feb 7, 2017 at 3:32 PM, Markus Metz
> > <markus.metz.giswork at gmail.com> wrote:
> > [...]
> > > Unfortunately it changes East from 179.9998611 to 179.9998597 and
north
> > > from 83.9998611 to 83.9998604.
> > >
> > > The more serious problem is that GRASS can not handle ll coordinates
like
> > > 180:0:0.50W or 90:0:0.5S.
> > >
> > > I have relaxed the ll restrictions in my local copy and can now import
> > > CHELSA and other for GRASS problematic ll datasets without getting
e.g. a
> > > narrow N-S strip, or GRASS fixing a subtle rounding error that in
fact is
> > > not an error. That means after each import I have to manually check if
> > > resolution and extents make sense, and if in doubt fix them with
r.region.
> >
> > That's probably rather more a power user task than common user
> > knowledge...
>
> Why a power user task? r.region is an easy to use module, as long as you
know the correct grid geometry. And with my relaxed ll restrictions I get
less errors and more usable results, in fact I need to use r.region less
often than before.
>
>
> Not sure that is what Markus meant, but "relaxed the restriction in my
local copy" sounds definitely like a power user task to me. If this is
something that can, and will, be done at the libgis level, great.

Fixing most of the ll wrap issues can be done at the libgis level. When I
wrote "relaxed the restriction in my local copy", I meant I would like to
commit by local changes, but would also like to know if it is ok to relax
the -180, 180 restriction for W-E and the -90, 90 restriction for S-N in
GRASS.

Issues as reported e.g. in tickets #352 and #2757 could easily be fixed
with r.region, but it would be much more convenient if there would be no
need to use r.region.

Markus M

> Otherwise, I would be interested to know how to do this.
>
>
> > Is there anything we could do at libgis level like
> > relaxing the ll restrictions along with appropriate user messages?
>
> Yes. The first points would be ll_scan.c, ll_format.c and adj_cellhd.c.
That should also remove cryptic errors like "ERROR: Syntax error in cell
header".
>
> > More and more global datasets are getting published, so the issue will
> > likely come up more frequently. Just to make it a bit easier :-)
>
> For a start, it would be nice if you can create a full SRTM mosaik (not
so new data) in GRASS.
>
> Markus M
>
> >
> > markusN
>
>
>
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