Hi,
I am new to GRASS but bought the book (3rd edition) and searched the
mail archive before sending in this question. The issue is about reading
a netCDF file: I got a "vertical mirror" of "upside down" effect (when I
display the imported raster using d.rast) but when I use an
old-fashioned technique (translating to GRASS ASCII, see below) it looks
okay.
The netCDF file itself is fine when viewed using, e.g., Ferret
(http://ferret.pmel.noaa.gov/Ferret/). The outputs of ncdump and
gdalinfo are provided at the end of this mail.
The best procedure would be to follow
http://lists.osgeo.org/pipermail/grass-user/2010-September/057799.html
and thus either use r.in.gdal directly:
grass>r.in.gdal -o NETCDF:"r2.nc":xe out=xe2
(in a WGS84 LOCATION) or after a gdal_translate:
grass>gdal_translate -a_srs EPSG:4326 NETCDF:"r2.nc":h0 h02.tiff
grass>r.in.gdal h02.tiff out=h02
But when I view the resulting raster, h02, it is flipped "upside
down" (as if the latitude was increasing "downward").
Thus so far I need to rely on a script which is actually a follow-up of
this (old) thread:
http://lists.osgeo.org/pipermail/grass-user/2002-December/008022.html
I have attached the script I use to this mail, in case somebody finds it
useful (you also need awk and nco); it is only an ersatz though, and I
would like to know what I can do to import my netCDF file directly into
GRASS (without a temporary GRASS ASCII file).
Are there metadata I should add to the netCDF file to get r.in.gdal
happy? Does r.in.gdal need a particular row order in the netCDF file
(such as j index increasing southward)?
That was a long one!
Hope it was more or less clear.
Nicolas
PS the system I am working with:
bash>uname -a
Linux Herminet1 2.6.32-25-generic #45-Ubuntu SMP Sat Oct 16 19:48:22 UTC
2010 i686 GNU/Linux
bash>gdalinfo --version
GDAL 1.6.3, released 2009/11/19
bash>grass -v
GRASS GIS 6.4.0RC5+39438
#####################
bash> ncdump -h r2.nc
netcdf r2 {
dimensions:
longitude = 133 ;
latitude = 64 ;
time = UNLIMITED ; // (14 currently)
variables:
double longitude(longitude) ;
longitude:units = "degrees_east" ;
double latitude(latitude) ;
latitude:units = "degrees_north" ;
double time(time) ;
time:units = "seconds since 1900-1-1" ;
float h0(latitude, longitude) ;
h0:units = "m" ;
h0:missing_value = -999.f ;
float xe(time, latitude, longitude) ;
xe:units = "m" ;
xe:missing_value = -999.f ;
float u(time, latitude, longitude) ;
u:units = "m/s" ;
u:missing_value = -999.f ;
float v(time, latitude, longitude) ;
v:units = "m/s" ;
v:missing_value = -999.f ;
// global attributes:
:Conventions = "COARDS" ;
}
####################
bash> gdalinfo r2.nc
Driver: netCDF/Network Common Data Format
Files: r2.nc
Size is 512, 512
Coordinate System is `'
Metadata:
NC_GLOBAL#Conventions=COARDS
Subdatasets:
SUBDATASET_1_NAME=NETCDF:"r2.nc":h0
SUBDATASET_1_DESC=[64x133] h0 (32-bit floating-point)
SUBDATASET_2_NAME=NETCDF:"r2.nc":xe
SUBDATASET_2_DESC=[14x64x133] xe (32-bit floating-point)
SUBDATASET_3_NAME=NETCDF:"r2.nc":u
SUBDATASET_3_DESC=[14x64x133] u (32-bit floating-point)
SUBDATASET_4_NAME=NETCDF:"r2.nc":v
SUBDATASET_4_DESC=[14x64x133] v (32-bit floating-point)
Corner Coordinates:
Upper Left ( 0.0, 0.0)
Lower Left ( 0.0, 512.0)
Upper Right ( 512.0, 0.0)
Lower Right ( 512.0, 512.0)
Center ( 256.0, 256.0)
(attachments)
nc2grass.sh (2.52 KB)