[GRASS-user] Re: Help - Output difference between ARCGIS enviroment settings and GRASS g.region function

[Markus Metz]

On Tue, May 8, 2012 at 6:27 PM, Alejandro Coca Castro <acocac at gmail.com> wrote:
> Hi, i forgot... below I have included the gdalinfo from both ouputs (ArcMap
> and GRASS). Any ideas as to what else I should check would be appreciated.
>
> #### ArcMap output gdalinfo ####
The extents and resolution seem to be written by ArcMap with single
precision. Can you write the raster out again with double precision?
More comments below.

> gdalinfo  x:\test\fileASC_ARCMAP.asc
> Driver: AAIGrid/Arc/Info ASCII Grid
> Files: x:\test\fileASC_ARCMAP.asc
>        x:\test\fileASC_ARCMAP.asc.aux.xml
> Size is 5245, 4800
> Coordinate System is `'

This
> Origin = (-60.925000056119998,-0.000000095999999)
> Pixel Size = (0.002083333330000,-0.002083333330000)

could also be in double precision
Origin = (-60.925000000000000,-0.000000000000000)
Pixel Size = (0.002083333333333,-0.002083333333333)

with pixel size equivalent to exactly 00:00:07.5

> Metadata:
>   PyramidResamplingType=NEAREST
> Corner Coordinates:

This
> Upper Left  ( -60.9250001,  -0.0000001)
> Lower Left  ( -60.9250001, -10.0000001)
> Upper Right ( -49.9979167,  -0.0000001)
> Lower Right ( -49.9979167, -10.0000001)
> Center      ( -55.4614584,  -5.0000001)

could also be in double precision

Upper Left  ( -60.9250000,  -0.0000000)
Lower Left  ( -60.9250000, -10.0000000)
Upper Right ( -49.9979167,  -0.0000000)
Lower Right ( -49.9979167, -10.0000000)
Center      ( -55.4614583,  -5.0000000)

The differences may seem small but can make a difference for a 5245x4800 raster.

Markus M


> Band 1 Block=5245x1 Type=Int32, ColorInterp=Undefined
>   NoData Value=-9999
> (Tue May 08 11:21:09 2012) Command finished (10
> sec)
> (Tue May 08 11:21:42 2012)
>
> #### GRASS output gdalinfo ####
> gdalinfo  x:\test\fileASC_GRASS.asc
> Driver: AAIGrid/Arc/Info ASCII Grid
> Files: x:\test\fileASC_GRASS.asc
>         x:\test\fileASC_GRASS.asc.aux.xml
> Size is 5246, 4801
> Coordinate System is `'
> Origin = (-60.927083000000003,0.000483000000001)
> Pixel Size = (0.002083000000000,-0.002083000000000)
> Metadata:
>   PyramidResamplingType=NEAREST
> Corner Coordinates:
> Upper Left  ( -60.9270830,   0.0004830)
> Lower Left  ( -60.9270830, -10.0000000)
> Upper Right ( -49.9996650,   0.0004830)
> Lower Right ( -49.9996650, -10.0000000)
> Center      ( -55.4633740,  -4.9997585)
> Band 1 Block=5246x1 Type=Int32, ColorInterp=Undefined
>   NoData Value=-9999
>
>
>
>
>
> 2012/5/8 Alejandro Coca Castro <acocac at 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 at default
>> g.region rast=fileTIF at default res=0.00208333333 align=MASK at default
>> r.mapcalc fileGRD = if(fileTIF at default  < 0 , null(), fileTIF at default)
>> r.out.arc input= fileGRD at 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
>
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