[gdal-dev] netCDF Data without subdatasets

Tue Aug 6 07:38:42 PDT 2013

Hi,

this is my first time using netcdf data and gdal library on Ubuntu 12.04

I have downloaded a subsetted monthly precipitation dataset from:

http://www.esrl.noaa.gov/psd/data/gridded/data.cmap.html

I want to create timelines of a few gridcells (covering germany)

As I understand, before converting bands to raster-images by 
gdal_translate one has to extract information from the subdatasets.

My Problem is:

using

gdalinfo X139.14.20.244.217.3.48.41.nc > gdalinfo.txt

No subdatasets appear. I would have expected something like to the 
follwing to be included in the output of gdalinfo:

SUBDATASET_1_NAME=NETCDF:...
SUBDATASET_1_DESC=...
SUBDATASET_2_NAME=...
SUBDATASET_2_DESC=...
SUBDATASET_3_NAME=...
SUBDATASET_3_DESC=...

Instead the output is as following:

Driver: netCDF/Network Common Data Format
Files: X139.14.20.244.217.3.47.29.nc
Size is 6, 5
Coordinate System is `'
Origin = (2.500000000000000,57.500000000000000)
Pixel Size = (2.500000000000000,-2.500000000000000)
Metadata:
   lat#actual_range={ 56.25, 46.25 }
   lat#axis=Y
   lat#long_name=Latitude
   lat#standard_name=latitude
   lat#units=degrees_north
   lon#actual_range={ 3.75, 16.25 }
   lon#axis=X
   lon#long_name=Longitude
   lon#standard_name=longitude
   lon#units=degrees_east
   NC_GLOBAL#Conventions=COARDS

NC_GLOBAL#documentation=http://www.esrl.noaa.gov/psd/data/gridded/data.cmap.html
   NC_GLOBAL#history=Tue Aug  6 03:47:30 2013: ncks -O -d 
lat,46.000000,57.000000 -d lon,3.000000,17.000000 -d time,0,2401 
/Datasets/cmap/std/precip.pentad.mean.nc 
/Public/www/X139.14.20.244.217.3.47.29.nc
Created by CAS 09/2012  using Version 1201
   NC_GLOBAL#platform=Analyses

NC_GLOBAL#references=http://www.esrl.noaa.gov/psd/data/gridded/data.cmap.html
   NC_GLOBAL#source=ftp ftp.cpc.ncep.noaa.gov precip/cmap/pentad
   NC_GLOBAL#title=CPC Merged Analysis of Precipitation Pentad data 
(excludes NCEP Reanalysis I)
   NC_GLOBAL#Version=V1201
   precip#actual_range={ 0, 25.07 }
   precip#add_offset=0
   precip#dataset=CPC Merged Analysis of Precipitation Standard
   precip#least_significant_digit=2
   precip#level_desc=Surface
   precip#long_name=Average Pentad Rate of Precipitation
   precip#missing_value=-9.96921e+36
   precip#parent_stat=Mean
   precip#precision=2
   precip#scale_factor=1
   precip#statistic=Pentad Mean
   precip#units=mm/day
   precip#valid_range={ 0, 250 }
   precip#var_desc=Precipitation
   time#actual_range={ 1569072, 1857384 }
   time#avg_period=0000-01-00 00:00:00
   time#axis=T
   time#delta_t=0000-00-05 00:00:00
   time#long_name=Time
   time#standard_name=time
   time#units=hours since 1800-01-01 00:00:0.0
Corner Coordinates:
Upper Left  (   2.5000000,  57.5000000)
Lower Left  (   2.5000000,  45.0000000)
Upper Right (  17.5000000,  57.5000000)
Lower Right (  17.5000000,  45.0000000)
Center      (  10.0000000,  51.2500000)
Band 1 Block=6x1 Type=Float32, ColorInterp=Undefined
   NoData Value=-9.96920996838686905e+36
   Metadata:
     actual_range={ 0, 25.07 }
     add_offset=0
     dataset=CPC Merged Analysis of Precipitation Standard
     least_significant_digit=2
     level_desc=Surface
     long_name=Average Pentad Rate of Precipitation
     missing_value=-9.96921e+36
     NETCDF_DIMENSION_time=1569072
     NETCDF_time_units=hours since 1800-01-01 00:00:0.0
     NETCDF_VARNAME=precip
     parent_stat=Mean
     precision=2
     scale_factor=1
     statistic=Pentad Mean
     units=mm/day
     valid_range={ 0, 250 }
     var_desc=Precipitation

And the next bands following.
---
Here is the metadata:
---

Metadata for /Public/www/X139.14.20.244.217.3.47.29.nc
Dimensions:

	time				2402
	lat				5
	lon				6
	precip				2402 5 6

Variables:

     time

     	long_name			Time
     	avg_period			0000-01-00 00:00:00
     	axis				T
     	standard_name			time
     	delta_t				0000-00-05 00:00:00
     	actual_range			1979-01-01 00:00:00 2011-11-22 00:00:00
     	units				hours since 1800-01-01 00:00:0.0
     lat

     	long_name			Latitude
     	axis				Y
     	standard_name			latitude
     	actual_range			56.25 46.25
     	units				degrees_north
     lon

     	long_name			Longitude
     	axis				X
     	standard_name			longitude
     	actual_range			3.75 16.25
     	units				degrees_east
     precip

     	parent_stat			Mean
     	long_name			Average Pentad Rate of Precipitation
     	valid_range			0 250
     	least_significant_digit		2
     	level_desc			Surface
     	dataset				CPC Merged Analysis of Precipitation Standard
     	missing_value			-9.96920996838687e+36
     	statistic			Pentad Mean
     	actual_range			0 25.0699996948242
     	var_desc			Precipitation
     	add_offset			0
     	precision			2
     	units				mm/day
     	scale_factor			1

Global Attributes:

     source
         ftp ftp.cpc.ncep.noaa.gov precip/cmap/pentad

     Version
         V1201

     history
         Tue Aug 6 03:47:30 2013: ncks -O -d lat,46.000000,57.000000 -d 
lon,3.000000,17.000000 -d time,0,2401 
/Datasets/cmap/std/precip.pentad.mean.nc 
/Public/www/X139.14.20.244.217.3.47.29.nc Created by CAS 09/2012 using 
Version 1201

     references
         http://www.esrl.noaa.gov/psd/data/gridded/data.cmap.html

     documentation
         http://www.esrl.noaa.gov/psd/data/gridded/data.cmap.html

     platform
         Analyses

     title
         CPC Merged Analysis of Precipitation Pentad data (excludes NCEP 
Reanalysis I)

     Conventions
         COARDS
---

Any advise on how to proceed to create rasters and timelines from this 
would be very appreciated. Probably something obvious I do not see.

Thanks,

Gunnar