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")
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"; ;
}
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