[gradsusr] Reading NetCDF files from AVHRR data

[James T. Potemra]

Hi Lance:

I don't think the issue is range, or any of the attributes, but rather 
the dimensions.  Check the top
of the netcdf file, and if you don't have latitude/longitude (looks like 
you have pixels and scans),
you'll have to create a ctl file that maps the dimensions that you do 
have onto the XDEF/YDEF
variables.   The documentation is here:
http://www.iges.org/grads/gadoc/gradcomdxdfopen.html

Jim



Lance Steele wrote:
>
> Hello everyone,
>
>  
>
> I would like to open NetCDF files converted from AVHRR data in GrADS. 
>  However, I am running into an error.
>
>  
>
> I am using the sat2netcdf utility from Weather Climate Toolkit (3.4.8) 
> to convert AVHRR files from the CLASS website (in .GC format) to 
> NetCDF.  However, when I try to open the .nc file in GrADS (v 2.0.a9 
> running on Mac OSX), I see the following error:
>
>  
>
> sdfopen ga-> sdfopen AVHRR.GC.nc
>
> Scanning self-describing file:  AVHRR.GC.nc
>
> gadsdf: SDF file has no discernable X coordinate.
>
>  
>
> One reason I think this is the problem is the lack of range.  For 
> example, when I do an ncdump on the AVHRR file, I see the following:
>
>  
>
> float lon(pixels, scans) ;
>
> lon:long_name = "Longitude" ;
>
> lon:units = "degrees_east" ;
>
> lon:_CoordinateAxisType = "Lon" ;
>
>  
>
> When I do an ncdump on a file that does open in GrADS, I see the 
> following:
>
>  
>
> float lon(lon) ;
>
>       lon:units = "degrees_east" ;
>
>       lon:long_name = "longitude" ;
>
>       lon:min_value = 120.f ;
>
>       lon:max_value = 139.7997f ;
>
>  
>
> Does GrADS require a range (min_value, max_value) to allow sdfopen to 
> work?  If so, how can I change the headers for lat and lon to include 
> a range?
>
>  
>
> Thank you,
>
>  
>
> Lance Steele
>
>  
>
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