[GRASS-dev] Re: g.region bugs [was: GRASS 6.3.0 release preparation]

[Maciej Sieczka]

Glynn Clements wrote:
> Maciej Sieczka wrote:
> 
>>>> hm, I disabled G_aling_window(), seems to work... (in CVS)
>>> Reverted in CVS.
>>>
>>> If the user specifies -a, the region should be aligned.
>> After Glynn reverted Martin's commit, I experience the
>> following:
>>
>> $ g.region n=5680980 s=5680960 w=602440 e=602480 res=20 -ag
>> n=5680980
>> s=5680960
>> w=602440
>> e=602480
>> nsres=20
>> ewres=20
>> rows=1
>> cols=2
>> cells=2
>>
>> $ echo "L 2 571600 5722275
>> 571610 5722275" | v.in.ascii -n out=line form=standard --o
>>
>> $ g.region vect=line res=1 -ag
>> ERROR: Invalid region: North must be larger than South
> 
> This is due to this change:
> 
> Index: lib/gis/align_window.c
> ===================================================================
> RCS file: /grassrepository/grass6/lib/gis/align_window.c,v
> retrieving revision 2.5
> retrieving revision 2.6
> diff -u -r2.5 -r2.6
> --- lib/gis/align_window.c	13 Apr 2007 22:42:58 -0000	2.5
> +++ lib/gis/align_window.c	15 Oct 2007 11:12:03 -0000	2.6
> @@ -49,9 +49,9 @@
>  
>      preserve = window->proj == PROJECTION_LL && window->east == (window->west+360);
>      window->south =
> -	G_row_to_northing (ceil(G_northing_to_row (window->south, ref)), ref);
> +	G_row_to_northing (floor(G_northing_to_row (window->south, ref)), ref);
>      window->north =
> -	G_row_to_northing (floor(G_northing_to_row (window->north, ref)), ref);
> +	G_row_to_northing (ceil(G_northing_to_row (window->north, ref)), ref);
>      window->east =
>  	G_col_to_easting (ceil(G_easting_to_col (window->east, ref)), ref);
>      window->west =
> 
> Originally, it rounded both edges outwards (i.e. north up, south
> down). The change makes it round inwards, so if it's less than a cell
> high, the north and south edges will be the wrong way around.
> 
> Reverted in CVS.

Thanks Glynn.

So, we are back to were it all started. More findings and
details follow.

Correction to original report - the bug *does* crop out in
GRASS 6.2.3 CVS too. However, differently. Please see:

The vector line is as follows:

$ echo "L 2 1
602473.66691719 5680962.45268225
602448.70284465 5680961.09147704
1 1" | v.in.ascii -n form=standard out=line



 IN GRASS 6.2.3 CVS:

$ g.region n=5680980 s=5680960 w=602440 e=602480 res=20 -a

$ g.region vect=line res=1 -ag
n=5680980
s=5680960
w=602440
e=602480
nsres=1
ewres=1
rows=20
cols=40

Wrong. But let's try again:

$ g.region vect=line res=1 -ag
n=5680963
s=5680961
w=602448
e=602474
nsres=1
ewres=1
rows=2
cols=26

Correct this time! Strange.



 IN GRASS 6.3 CVS:

$ g.region n=5680980 s=5680960 w=602440 e=602480 res=20 -a

$ g.region vect=line res=1 -ag
n=5680963
s=5680942
w=602448
e=602489
nsres=1
ewres=1
rows=21
cols=41
cells=861

Wrong, though different than the first try in 6.2.3 CVS (see
above). But let's try again:

$ g.region vect=line res=1 -ag
n=5680963
s=5680960
w=602448
e=602474
nsres=1
ewres=1
rows=3
cols=26
cells=78

Closer, but still wrong. s should be 5680961.

Maciek