As I understand, setting the a flag when defining a region should maintain the original resolution. So when setting different bounds based on a vector layer and with the a flag set, I would expect exactly the same resolution. Yet, the below output shows that this is not the case (even though differences are small). Am I misunderstanding something?
GRASS 7.3.svn (Latlon):~ > g.region -g
projection=3
zone=0
n=10
s=0
w=-80
e=-70
nsres=0.00025
ewres=0.00025
rows=40000
cols=40000
cells=1600000000
GRASS 7.3.svn (Latlon):~ > g.region -a vector=pastures
On Fri, Dec 23, 2016 at 3:54 PM, Paulo van Breugel
<p.vanbreugel@gmail.com> wrote:
Dear devs,
As I understand, setting the a flag when defining a region should maintain
the original resolution. So when setting different bounds based on a vector
layer and with the a flag set, I would expect exactly the same resolution.
... I think only, when you also use the res=xxx parameter.
https://grass.osgeo.org/grass72/manuals/g.region.html#notes
"With the -a flag all four boundaries are adjusted to be even
multiples of the resolution, aligning the region to the resolution
supplied by the user. The default is to align the region resolution to
match the region boundaries. "
Strange, the behaviour I described only happens in one particular map set I was working in yesterday. I have tried out in different map sets now, and there it works as I expected, i.e., no need to supply the res=value argument. This is how I always assumed, and would hope, it to work. So depending on the intended behaviour, perhaps the note should be changed to:
ยทยทยท
On 23-12-16 16:00, Markus Neteler wrote:
On Fri, Dec 23, 2016 at 3:54 PM, Paulo van Breugel
[<p.vanbreugel@gmail.com>](mailto:p.vanbreugel@gmail.com) wrote:
Dear devs,
As I understand, setting the a flag when defining a region should maintain
the original resolution. So when setting different bounds based on a vector
layer and with the a flag set, I would expect exactly the same resolution.
... I think only, when you also use the res=xxx parameter.
[https://grass.osgeo.org/grass72/manuals/g.region.html#notes](https://grass.osgeo.org/grass72/manuals/g.region.html#notes)
"With the -a flag all four boundaries are adjusted to be even
multiples of the resolution, aligning the region to the resolution
supplied by the user. The default is to align the region resolution to
match the region boundaries. "
Please try along with the res=value.
Markus
# setting region based on vector > g.region save=test > g.region vector=test > g.region -g projection=99 zone=0 n=226729.31747673 s=216615.56359876 w=630721.30299897 e=643766.80455016 nsres=10.00371303 ewres=9.99655291 rows=1011 cols=1305 cells=1319355
# resetting region, and then setting based on vector with a flag > g.region region=test > g.region -a vector=test > g.region -g projection=99 zone=0 n=226730 s=216610 w=630720 e=643770 nsres=10 ewres=10 rows=1012 cols=1305 cells=1320660
"By default the region resolution is aligned to match the region boundaries. With the -a flag all four boundaries are adjusted to be even multiples of the resolution, aligning the region to the resolution supplied by the user (res=xxx), or, if not supplied, to the current resolution"
On Sat, Dec 24, 2016 at 10:40 AM, Paulo van Breugel
<p.vanbreugel@gmail.com> wrote:
...
So depending on
the intended behaviour, perhaps the note should be changed to:
"By default the region resolution is aligned to match the region boundaries.
With the -a flag all four boundaries are adjusted to be even multiples of
the
resolution, aligning the region to the resolution supplied by the user
(res=xxx), or, if not supplied, to the current resolution"
From this text change it is not obvious to me what to remove and what to keep.
On Wed, Dec 28, 2016 at 4:21 PM, Markus Neteler <neteler@osgeo.org> wrote:
On Sat, Dec 24, 2016 at 10:40 AM, Paulo van Breugel
<p.vanbreugel@gmail.com> wrote:
...
> So depending on
> the intended behaviour, perhaps the note should be changed to:
>
> "By default the region resolution is aligned to match the region
boundaries.
> With the -a flag all four boundaries are adjusted to be even multiples of
> the
> resolution, aligning the region to the resolution supplied by the user
> (res=xxx), or, if not supplied, to the current resolution"
From this text change it is not obvious to me what to remove and what to
keep.
Please send a diff, thanks.
Sorry for late response, was away. It seems the discussion on this topic is
ongoing, so let's see how that concludes