[GRASS-user] raster pixel value

[Nikos Alexandris]

Following up, why are there differences between GDAL and GRASS GIS in
the following example?

This ftp://ftp.soilgrids.org/data/aggregated/5km/OCDENS_M_sl1_5km_ll.tif
raster map, subject to `gdalinfo`:
```
gdalinfo OCDENS_M_sl1_5km_ll.tif -nogcp -nomd -norat -noct -nofl
Driver: GTiff/GeoTIFF
Files: OCDENS_M_sl1_5km_ll.tif
Size is 7200, 2987
Coordinate System is:
GEOGCS["WGS 84",
    DATUM["WGS_1984",
        SPHEROID["WGS 84",6378137,298.257223563,
            AUTHORITY["EPSG","7030"]],
        AUTHORITY["EPSG","6326"]],
    PRIMEM["Greenwich",0],
    UNIT["degree",0.0174532925199433],
    AUTHORITY["EPSG","4326"]]
Origin = (-180.000000000000000,87.370000000000005)
Pixel Size = (0.050000000000000,-0.050000000000000)
Corner Coordinates:
Upper Left  (-180.0000000,  87.3700000) (180d 0' 0.00"W, 87d22'12.00"N)
Lower Left  (-180.0000000, -61.9800000) (180d 0' 0.00"W, 61d58'48.00"S)
Upper Right ( 180.0000000,  87.3700000) (180d 0' 0.00"E, 87d22'12.00"N)
Lower Right ( 180.0000000, -61.9800000) (180d 0' 0.00"E, 61d58'48.00"S)
Center      (   0.0000000,  12.6950000) (  0d 0' 0.00"E, 12d41'42.00"N)
Band 1 Block=7200x1 Type=Int16, ColorInterp=Gray
  NoData Value=-32768
```

and GRASS GIS
```
# create a new Location
grass -c OCDENS_M_sl1_5km_ll.tif /geoyeux/grassdb/global/soil_grids/

# projection info
g.proj -g

name=WGS 84
datum=wgs84
ellps=wgs84
proj=ll
no_defs=defined
epsg=4326
unit=degree
units=degrees
meters=1.0

# raster info
r.info -g OCDENS_M_sl1_5km_ll

north=87.37
south=-61.98
east=180
west=-180
nsres=0.05
ewres=0.05
rows=2987
cols=7200
cells=21506400
datatype=CELL
ncats=0

# report non-NULL cells and their x, y grid location
r.stats OCDENS_M_sl1_5km_ll -n -x > stats_x
```

Comparing a few single pixels via:
```
while read LINE;do
    set -- $LINE
    echo " ($1,$2)
    echo "GDAL:  $(gdallocationinfo -valonly OCDENS_M_sl1_5km_ll.tif $1 $2)"
    echo "GRASS: $3"
    echo
done < stats_x_head
```

gives
```
 (2930,77)
GDAL:  2090
GRASS: 2096

 (2931,77)
GDAL:  2055
GRASS: 2090

 (2932,77)
GDAL:  2063
GRASS: 2055

 (2933,77)
GDAL:  2093
GRASS: 2063

 (2934,77)
GDAL:  2240
GRASS: 2093

 (2935,77)
GDAL:  2332
GRASS: 2240

 (2936,77)
GDAL:  2296
GRASS: 2332

 (2937,77)
GDAL:  2253
GRASS: 2296

 (2938,77)
GDAL:  2179
GRASS: 2253

 (2939,77)
GDAL:  2115
GRASS: 2179
```

Why these differences?

Nikos


# meta

GRASS 7.7.svn (2019)
libgis Revision: 74118
libgis Date: 2019-02-21 10:38:28 +0100 (Thu, 21 Feb 2019)

GDAL 2.3.1, released 2018/06/22