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20050309: Netcdf Radar Files in IDV

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  • Subject: 20050309: Netcdf Radar Files in IDV
  • Date: Fri, 11 Mar 2005 12:36:14 -0700
>From: Ryan May <address@hidden>
>Organization: OU
>Keywords: 200503091739.j29HdPv2028745  IDV netcdf sweep file

Hi Ryan-

>A sample file is attached.

Thanks.  It uncovered a couple of problems that I was able to
work around.  The big problem is that there are no units specified
for the following variables:

        int base_time ;
        double Latitude ;
        double Longitude ;
        double Altitude ;
        float Cell_Spacing ;
        float Range_to_First_Cell ;
        float Azimuth(Time) ;
        float Elevation(Time) ;
        float Nyquist(Time) ;
        float RadialTime(Time) ;
        int NumberPulses(Time) ;
        float PRF(Time) ;
        int PPIRadialNumber(Time) ;
        int VolumeRadialNumber(Time) ;
        float BeamSpacing(Time) ;

Best practices for netCDF files encourage using units when
they are known.  For now, I'm assuming standard units these
variables as follows:

base_time             - seconds since 1970-01-01 00:00:00;
Latitude              - degrees_north
Longitude             - degrees_east
Altitude              - meters
Cell_Spacing          - meters
Range_to_First_Cell   - meters
Azimuth(Time)         - degrees
Elevation(Time)       - degrees

>I want to reiterate that part of my problem was that the input routines 
>for netcdf sweepfiles assumed that the data was stored as short 
>integers, which caused an exception when reading the data I had stored 
>as floats.  Writing my data in a packed format was a way I tried to 
>circumvent that limitation.  I personally think it is more routine for 
>data to be stored as floats, and that the IDV needs to be able to read 
>floating point netcdf radar data without problems.

Okay, I misunderstood.  The new code should handle either packed
shorts or floats.  If you have a file with the values in floats,
please send that along.

Thanks.

Don Murray
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