Problems in displaying netCDF files with GrADS

[Don Hooper]

This is the expected behavior.  The sdfopen interface supports unpacked
data variables of type "float" (a 32 bit type).  I *think* it supports
unpacked "double" data variables, thanks to some implicit magic in the NetCDF
library.  It also supports 16 bit integer data variables ("Shorts") that
are packed in the standard NetCDF sense and thus represent 32 bit floating
point values.  Nothing else is supported by the sdfopen interface.  In fact,
Unidata has been discouraging folks from using the "byte" type for years,
saying that the implementation was likely to change at some point in the
future.  Was I the only one who took 'em seriously?  ;)

-Hoop
> From owner-gradsusr at LIST.CINECA.IT  Fri Jan 14 20:36:39 2005
> From: Fred Yongxin Zhang <yongxinz at HAWAII.EDU>
>
> Dear GrADS users,
>
>    I tried displaying netCDF files with GrADS v1.8SL9 but I encountered
> some problems. Please refer to the attached information. I searched the
> online archive but did not find solutions to these problems. Your
> suggestions are greatly appreciated.
>
> Thanks,
> Fred
>
> ***************Return from "ncdump -h" is as follows***************
> netcdf 20041030_1030 {
> dimensions:
>         y = 512 ;
>         x = 1024 ;
>
> variables:
>         byte image(y, x) ;
>         double validTime ;
>                 validTime:units = "seconds since 1970-1-1 00:00:00.00
> 0:00" ;
>                 validTime:long_name = "Valid Time" ;
>         byte valid100thSecs ;
>                 valid100thSecs:units = "centiseconds" ;
>                 valid100thSecs:long_name = "Valid 100th of a second" ;
>
> // global attributes:
>                 :channel = "Visible" ;
>                 :depictorName = "nh2Sat at 18316368" ;
>                 :projIndex = 1 ;
>                 :projName = "STEREOGRAPHIC" ;
>                 :centralLat = 90.f ;
>                 :centralLon = -105.f ;
>                 :rotation = 0.f ;
>                 :xMin = -1.0335739f ;
>                 :xMax = 1.0335791f ;
>                 :yMin = -1.0335739f ;
>                 :yMax = 0.f ;
>                 :lat00 = -1.8917102f ;
>                 :lon00 = 165.f ;
>                 :latNxNy = -21.245136f ;
>                 :lonNxNy = -59.999855f ;
>                 :dxKm = 20.313013f ;
>                 :dyKm = 20.332838f ;
>                 :latDxDy = 35.341339f ;
>                 :lonDxDy = -104.99971f ;
> }
>
> *********************My data descriptor file looks like this**********
> dset ^20041030_1030
> title This file contains the satellite data
> undef 99999.0
> xdef x 1024 LINEAR 0.0 .25
> ydef y 512 LINEAR 0.0 .25
> vars 1
> image=>image 0 512 1024 satellite data
> endvars
>
> ********************The error message looks like this******************
> ga-> xdfopen 20041030_1030.ctl
> Scanning Descriptor File:  20041030_1030.ctl
> SDF file has no discernable time coordinate.
> Found displayable variable image with 0 levels in SDF file.
> Data file 20041030_1030 is open as file 1
> LON set to 0 255.75
> LAT set to 0 127.75
> LEV set to 0 0
> Time values set: 1:1:1:0 1:1:1:0
> ga-> d image
> SDF data variable has unsupported packed data type.
> Data Request Error:  Error for variable 'image'
>   Error ocurred at column 1
> DISPLAY error:  Invalid expression
>   Expression = image
> ga->
> ***********************************************************************