On Tue, May 8, 2012 at 9:41 PM, Alejandro Coca Castro <acocac@gmail.com> wrote:
Hi Mark, i followed your instructions, so i put in command-line
This
g.region rast=MASK@default nsres=0:00:07.5 ewres=0:00:07.5
will adjust, i.e. modify the resolution in order to fit into the
extents. The extents are not modified. In GRASS, the extents have
precedence over resolution, unless you use the -a flag, in which case
the extents are aligned to the desired resolution. Thus use either
g.region rast=MASK@default nsres=0:00:07.5 ewres=0:00:07.5 -a
to align the current region to the desired resolution and enforcing
this resolution, or
g.region rast=MASK@default
You can check if the current region is all right with g.region -p or
g.region -g, before doing any processing.
I tried to set the region with the gdalinfo output of the ArcMap
raster fileASC_ARCMAP.asc:
g.region w=-60.9250001 e=-49.9979167 n=-0.0000001 s=-10.0000001
res=0.00208333333
Output of g.region -g:
n=-1e-07
s=-10.0000001
w=-60.9250001
e=-49.9979167
nsres=0.00208333333333333
ewres=0.00208333334604385
rows=4800
cols=5245
cells=25176000
As you can see, the resolution needed to be adjusted, i.e. there are
floating point rounding errors in fileASC_ARCMAP.asc. Using rounded
DD:MM:SS.S format:
g.region w=60:55:30W e=49:59:52.5W n=0 s=10S res=00:00:07.5
Output of g.region -g:
n=0
s=-10
w=-60.925
e=-49.9979166666667
nsres=0.00208333333333333
ewres=0.00208333333333333
rows=4800
cols=5245
cells=25176000
This is probably the desired extents and resolution, the resolution
did not need to be adjusted (0.00208333333333333 = 00:00:07.5) .
Markus M
Now, I get the same number of columns and rows. However, the cell size isn't
the same that ArcMAP output file...so i think it can be the reason of
non-similar extend and origin....
Below i show you the output gdalinfo,
Driver: AAIGrid/Arc/Info ASCII Grid
Files: D:\gras_data\temp\test5.asc
Size is 5245, 4800
Coordinate System is `'
Origin = (-60.924999999999997,-0.001600000000000)
Pixel Size = (0.002083000000000,-0.002083000000000)
Corner Coordinates:
Upper Left ( -60.9250000, -0.0016000)
Lower Left ( -60.9250000, -10.0000000)
Upper Right ( -49.9996650, -0.0016000)
Lower Right ( -49.9996650, -10.0000000)
Center ( -55.4623325, -5.0008000)
Band 1 Block=5245x1 Type=Int32, ColorInterp=Undefined
NoData Value=-9999
Do you have others ideas?
------
Jacquie, thanks for your comments, i hope the next SPs versions fix these
kind of bugs.
regards,
2012/5/8 Alejandro Coca Castro <acocac@gmail.com>
Hi, i tried to convert the following enviroments settings to GRASS
g.region and r.mask for the next ARCGIS output (ASCII file):
fileTIF = r"x:\\test\\fileTIF\.tif"
MASK = r"x:\\test\\mask\_file"
env\.extent = fileTIF
env\.snapRaster = MASK
env\.mask = MASK
fileGRD = r"x:\\test\\fileGRD"
outCon = Con\(fileTIF, fileTIF, "", "VALUE >= 0"\)
outCon\.save\(fileGRD\)
fileASC = r"x:\\test\\fileASC\.asc"
env\.workspace = fileGRD
RasterToASCII\_conversion\(fileGRD,fileASC\)
So, i put on the GRASS command-line:
r.mask input=mask_file@default
g.region rast=fileTIF@default res=0.00208333333 align=MASK@default
r.mapcalc fileGRD = if(fileTIF@default < 0 , null(), fileTIF@default)
r.out.arc input= fileGRD@default output=x:\test\fileASC_grass.asc
However, the ArcGIS and GRASS outputs had a different extend and curiously
the GRASS output didn't snap their cells with the MASK. Also, when i observe
the GRASS output cellsize, it only has the first 6 decimals (f.e.
0.002083)....
Finally i tried to setup the parameters of g.region with the ArcGIS output
but GRASS output definetly didnt have the same properties of ArcGIS output
(cellsize, columns and rows, extend)
If somebody knows how can i fix it, i'll be grateful,
Thanks in advance,
Alejandro
--
Alejandro Coca Castro
