[R-sig-Geo] Problems reading netcdf with RGDAL
Roger Bivand
Roger.Bivand at nhh.no
Thu Jan 7 18:16:27 CET 2010
On Thu, 7 Jan 2010, Middel, Kevin (MNR) wrote:
> Hi,
>
> I am trying to read a netcdf file and create spatial grid files
> compatible with a GIS from the various time arrays, but ran into a
> problem right off with rgdal. The .nc file contains daily air
> temperatures across North America for a given year.
>
>
>
> Using the command:
>> GDALinfo("air.2m.1979.nc")
Where is your sessionInfo() information? Does gdalDrivers() include the
NetCDF driver (no, you are on Windows using the standard binary rgdal
package - guesses based on the file path quoted below)? Have you read
file.show(system.file("README.windows", package="rgdal")), which tells you
how to install rgdal from source on Windows to access extra drivers
depending on external software?
The user needing more exotic drivers (those not provided by GDAL itself)
has to provide the external dependencies and install from the source
package on all platforms. If ncdf can import the data, please use that if
you do not want to install rgdal from source.
Hope this helps,
Roger
>
>
> I get the error:
> CPL ERROR 4: `air.2m.1979.nc' not recognised as a supported file format.
>
>
>
> Error in .local(.Object, ...) :
>
> `air.2m.1979.nc' not recognised as a supported file format.
>
>
>
> I am able read the file using the package ncdf, and the utility ncdump,
> as well as view the data in panoply, so I'm not sure what I'm doing
> incorrectly. I've also tried using FWTools to view the data and in
> this program the image is inverted (N-S). Finally I've had a look at
> the data using GDALInfo installed with FWTools and have pasted the
> output below, as well as the output from NCDump.
>
>
>
> It's probably pretty obvious that I'm new to this format, so any
> help/guidance anyone can provide would be greatly appreciated.
>
>
>
> Thanks in advance,
>
> Kevin
>
>
>
> GDALInfo Output:
>
>
>
> Driver: netCDF/Network Common Data Format
>
> Files: d:\databases\climate\narr\air.2m.1979.nc
>
> Size is 512, 512
>
> Coordinate System is `'
>
> Metadata:
>
> NC_GLOBAL#standardpar1=50
>
> NC_GLOBAL#standardpar2=50
>
> NC_GLOBAL#centerlon=-107
>
> NC_GLOBAL#centerlat=50
>
> NC_GLOBAL#latcorners=1.000001e+000, 8.979450e-001, 4.635440e+001,
> 4.663433e+001
>
> NC_GLOBAL#loncorners=-1.455000e+002, -6.832005e+001, -2.569891e+000,
> 1.486418e+002
>
> NC_GLOBAL#stream=s1
>
> NC_GLOBAL#title=Daily NARR
>
> NC_GLOBAL#Conventions=CF-1.0
>
> NC_GLOBAL#history=On Thu Feb 9 16:48:19 2006 single precision time
> renamed oldtime,
>
> values transferred to double precision new time variable.
>
> created 2005 by Jeff Whitaker
>
> NC_GLOBAL#institution=National Centers for Environmental Prediction
>
> NC_GLOBAL#platform=Model
>
>
> NC_GLOBAL#references=http://wwwt.emc.ncep.noaa.gov/mmb/rreanl/index.html
>
> http://www.cdc.noaa.gov/cdc/data.narr.html
>
> Subdatasets:
>
>
> SUBDATASET_1_NAME=NETCDF:"d:\databases\climate\narr\air.2m.1979.nc":lat
>
> SUBDATASET_1_DESC=[277x349] latitude (32-bit floating-point)
>
>
> SUBDATASET_2_NAME=NETCDF:"d:\databases\climate\narr\air.2m.1979.nc":lon
>
> SUBDATASET_2_DESC=[277x349] longitude (32-bit floating-point)
>
>
> SUBDATASET_3_NAME=NETCDF:"d:\databases\climate\narr\air.2m.1979.nc":time
> _bnds
>
> SUBDATASET_3_DESC=[365x2] time_bnds (64-bit floating-point)
>
>
> SUBDATASET_4_NAME=NETCDF:"d:\databases\climate\narr\air.2m.1979.nc":air
>
> SUBDATASET_4_DESC=[365x277x349] air_temperature (8-bit integer)
>
> 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)
>
>
>
>
>
> NCDump Output:
>
>
>
> netcdf air.2m.1979 {
>
> dimensions:
>
> time = UNLIMITED ; // (365 currently)
>
> y = 277 ;
>
> x = 349 ;
>
> nbnds = 2 ;
>
> variables:
>
> float lat(y, x) ;
>
> lat:long_name = "latitude coordinate" ;
>
> lat:units = "degrees_north" ;
>
> lat:axis = "Y" ;
>
> lat:coordinate_defines = "point" ;
>
> lat:standard_name = "latitude" ;
>
> float lon(y, x) ;
>
> lon:units = "degrees_east" ;
>
> lon:long_name = "longitude coordinate" ;
>
> lon:axis = "X" ;
>
> lon:coordinate_defines = "point" ;
>
> lon:standard_name = "longitude" ;
>
> float x(x) ;
>
> x:long_name = "eastward distance from southwest corner
> of domain in projection coordinates" ;
>
> x:units = "m" ;
>
> x:standard_name = "projection_x_coordinate" ;
>
> float y(y) ;
>
> y:long_name = "northward distance from southwest corner
> of domain in projection coordinates" ;
>
> y:units = "m" ;
>
> y:standard_name = "projection_y_coordinate" ;
>
> int Lambert_Conformal ;
>
> Lambert_Conformal:grid_mapping_name =
> "lambert_conformal_conic" ;
>
> Lambert_Conformal:standard_parallel = 50., 50. ;
>
> Lambert_Conformal:longitude_of_central_meridian = -107.
> ;
>
> Lambert_Conformal:latitude_of_projection_origin = 50. ;
>
> Lambert_Conformal:false_easting = 5632642.22547 ;
>
> Lambert_Conformal:false_northing = 4612545.65137 ;
>
> double time(time) ;
>
> time:units = "hours since 1800-1-1 00:00:0.0" ;
>
> time:long_name = "analysis time" ;
>
> time:axis = "T" ;
>
> time:standard_name = "time" ;
>
> time:coordinate_defines = "start" ;
>
> time:delta_t = "0000-00-01 00:00:00" ;
>
> time:actual_range = 1569072., 1577808. ;
>
> time:avg_period = "0000-00-01 00:00:00" ;
>
> double time_bnds(time, nbnds) ;
>
> time_bnds:long_name = "Time Boundaries" ;
>
> short air(time, y, x) ;
>
> air:units = "K" ;
>
> air:long_name = "Daily Air Temperature at 2 m" ;
>
> air:unpacked_valid_range = 151.f, 400.f ;
>
> air:precision = 0.003799786f ;
>
> air:actual_range = 219.7989f, 312.3237f ;
>
> air:missing_value = 32767s ;
>
> air:valid_range = -32765s, 32765s ;
>
> air:_FillValue = -32767s ;
>
> air:GRIB_name = "TMP" ;
>
> air:GRIB_id = 11 ;
>
> air:var_desc = "Air temperature" ;
>
> air:standard_name = "air_temperature" ;
>
> air:level_desc = "2 m" ;
>
> air:dataset = "NARR Daily Averages" ;
>
> air:statistic = "Mean" ;
>
> air:parent_stat = "Individual Obs" ;
>
> air:grid_mapping = "Lambert_Conformal" ;
>
> air:coordinates = "lat lon" ;
>
> air:add_offset = 275.5f ;
>
> air:scale_factor = 0.003799786f ;
>
> air:cell_methods = "time: mean (of 8 3-hourly values in
> one day)" ;
>
>
>
> // global attributes:
>
> :standardpar1 = 50. ;
>
> :standardpar2 = 50.000001 ;
>
> :centerlon = -107. ;
>
> :centerlat = 50. ;
>
> :latcorners = 1.000001f, 0.897945f, 46.3544f, 46.63433f
> ;
>
> :loncorners = -145.5f, -68.32005f, -2.569891f, 148.6418f
> ;
>
> :stream = "s1" ;
>
> :title = "Daily NARR" ;
>
> :Conventions = "CF-1.0" ;
>
> :history = "On Thu Feb 9 16:48:19 2006 single precision
> time renamed oldtime,\n",
>
> "values transferred to double precision new time
> variable.\n",
>
> "created 2005 by Jeff Whitaker" ;
>
> :institution = "National Centers for Environmental
> Prediction" ;
>
> :platform = "Model" ;
>
> :references =
> "http://wwwt.emc.ncep.noaa.gov/mmb/rreanl/index.html\n",
>
> "http://www.cdc.noaa.gov/cdc/data.narr.html" ;
>
> }
>
>
>
>
>
>
>
>
> [[alternative HTML version deleted]]
>
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>
--
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no
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