[gdal-dev] gdal, netCDF and projection

[Roger André]

Hi all,

Just a couple quick netCDF related questions:

1)  Is there any way to include projection information in a netCDF
file so that gdal can properly read it?  It appears that
georeferencing is handled correctly, but not projection info.  This
causes problems with the whole "north/south origin shift" between the
netCDF and other raster formats when gdal is used to convert the .nc
file into a GeoTIFF.  Most notably, I'm not sure how to assign the
data a projection - either for display in MapServer, or to reproject
it to EPSG:4326:  See example below.

File created with ArcGIS 9.3:
$ gdalinfo fwdir_bas.nc
Driver: netCDF/Network Common Data Format
Files: fwdir_bas.nc
Size is 42000, 42000
Coordinate System is `'
Origin = (65.000000000000000,5.000000000028436)
Pixel Size = (0.000833333333333,0.000833333333333)
Metadata:
  NC_GLOBAL#Conventions=CF-1.0
  NC_GLOBAL#Source_Software=ESRI ArcGIS
  Fwdir_bas#long_name=Fwdir_bas
 Fwdir_bas#esri_pe_string=GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]]
  Fwdir_bas#coordinates=lon lat
  Fwdir_bas#units=Degree
  Fwdir_bas#missing_value=
  lon#long_name=longitude coordinate
  lon#standard_name=longitude
  lon#units=degrees_east
  lat#long_name=latitude coordinate
  lat#standard_name=latitude
  lat#units=degrees_north
Corner Coordinates:
Upper Left  (  65.0000000,   5.0000000)
Lower Left  (  65.0000000,  40.0000000)
Upper Right ( 100.0000000,   5.0000000)
Lower Right ( 100.0000000,  40.0000000)
Center      (  82.5000000,  22.5000000)
Band 1 Block=42000x1 Type=Byte, ColorInterp=Undefined
  NoData Value=0
  Metadata:
    NETCDF_VARNAME=Fwdir_bas

- After translation to GeoTIFF:

$ gdalinfo fwdir_bas.tif
Driver: GTiff/GeoTIFF
Files: fwdir_bas.tif
Size is 42000, 42000
Coordinate System is `'
Origin = (65.000000000000000,5.000000000028436)
Pixel Size = (0.000833333333333,0.000833333333333)
Metadata:
  NC_GLOBAL#Conventions=CF-1.0
  NC_GLOBAL#Source_Software=ESRI ArcGIS
  Fwdir_bas#long_name=Fwdir_bas
  Fwdir_bas#esri_pe_string=GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]]
  Fwdir_bas#coordinates=lon lat
  Fwdir_bas#units=Degree
  lon#long_name=longitude coordinate
  lon#standard_name=longitude
  lon#units=degrees_east
  lat#long_name=latitude coordinate
  lat#standard_name=latitude
  lat#units=degrees_north
Image Structure Metadata:
  INTERLEAVE=BAND
Corner Coordinates:
Upper Left  (  65.0000000,   5.0000000)
Lower Left  (  65.0000000,  40.0000000)
Upper Right ( 100.0000000,   5.0000000)
Lower Right ( 100.0000000,  40.0000000)
Center      (  82.5000000,  22.5000000)
Band 1 Block=42000x1 Type=Byte, ColorInterp=Gray
  NoData Value=0
  Metadata:
    NETCDF_VARNAME=Fwdir_bas

2)  Is there any continuing work being done in the gdal community with
regards to the GALEON project?  As far as I can see, all gdal posts
related to this are from 2005 - 2006, yet recent articles in some
industry rags suggest that GALEON is still on the OGC's radar.  I'd be
interested in working on this with anyone else who already is to help
resolve some of the remaining hiccups that are left in getting netCDF
files to work more easily with gdal.  Feel free to contact me off-list
regarding this.

Roger