problem display contents in hdf file

[li zhao]

Hi Brian,

I think the problem is not with scale_factor and
add_off. Also, I did  "ncdump" on that hdf file and
figured out the variables and included them in the ctl
file when I posted my question in the previous mail.

Infact I ran this script on GrADS v1.9b4 on alpha
machine. However when I run the same version of grads
on LINUX X86_64, the script gives error messages as I
mentioned in the last mail.


For your information I am attaching the errors again:
 ga-> d lst_day_cmg
HDF-SDS Read Error for dtype UINT16
Data Request Error:  Error for variable 'lst_day_cmg'
Error ocurred at column 1
DISPLAY error:  Invalid expression
Expression = lst_day_cmg


Please also see the attached ctl file:


 ***********************************************
 dset ^MOD11C3.A2000061.004.2004116185101.hdf
 dtype hdfsds
 options yrev
 undef 0s
 unpack scale_factor add_off
 xdef 7200 linear -180.0 0.05
 ydef 3600 linear  -90.0 0.05
 zdef 1 levels 1
 tdef 1 linear 1jan1989 1dy
 vars 16
 LST_Day_CMG=>lst_day_cmg 1 z,y,x Monthly daytime
 3min
 CMG Land-surface Temperature
 QC_Day=>qc_day 0 y,x Sea surface temperature
 Day_view_time=>day_view_time 0 y,x Sea surface
 temperature
 Day_view_angl=>day_view_angl 0 y,x Sea surface
 temperature
 Clear_sky_days=>clear_sky_days 0 y,x Sea surface
 temperature
 LST_Night_CMG=>lst_night_cmg 0 y,x Sea surface
 temperature
 QC_Night=>qc_night 0 y,x Sea surface temperature
 Night_view_time=>night_view_time 0 y,x Sea surface
 temperature
 Night_view_angl=>night_view_angl 0 y,x Sea surface
 temperature
 Clear_sky_Night=>clear_sky_night 0 y,x Sea surface
 temperature
 Emis_20=>emis_20 0 y,x Sea surface temperature
 Emis_22=>emis_22 0 y,x Sea surface temperature
 Emis_23=>emis_23 0 y,x Sea surface temperature
 Emis_29=>emis_29 0 y,x Sea surface temperature
 Emis_31=>emis_31 0 y,x Sea surface temperature
 Emis_32=>emis_32 0 y,x Sea surface temperature
 endvars
***********************************************************************

regards
Zhao

--- brian vant-hull <brianvanthull at YAHOO.COM> wrote:

> Zhao;
> 'scale_factor' and 'add_off' are just example
> variables in user's guide.  You have to provide
> names
> that are spelled exactly as they appear in the hdf
> file.  Unfortunately these names often change
> depending on the variable within each file!  In that
> case you'd have to open the file separately for each
> variable.
>
> I don't know if there's a way to have GrADS dump the
> variable names so you can put them in the ctl file.
> If not, IDL and Matlab have built in functions, and
> you can download libraries to read hdf in C or
> Fortran.  Or just ask someone else who's figured out
> how to use your particular dataset.  Once you have
> the
> correct names for the offset and scale you are good
> to
> go.
>
> Anybody who has worked with hdf before should be
> able
> to give you something that will get the variable
> names
> for you, but it's a multiple step process or
> program.
> If you have IDL or Matlab go to
> http://www.atmos.umd.edu/~gcm and click on the blue
> useful button, then go down to the link about
> reading
> hdf in matlab and IDL.  This will show you how to go
> about it.
>
> -Brian.
>
> --- li zhao <janelizhao at YAHOO.COM> wrote:
>
> > Hi everybody,
> >
> > Probably this is a simple fix but I must be
> missing
> > something. I try to open a hdf file and it loads
> > well,
> > but giving the following error message when
> > displaying
> > the variable.
> >
> > ga-> d lst_day_cmg
> > Warning: HDF attribute named "add_off" does not
> > exist
> > Warning: Could not retrieve "add_off" -- setting
> to
> > 0.0
> > HDF-SDS Read Error for dtype UINT16
> > Data Request Error:  Error for variable
> > 'lst_day_cmg'
> >   Error ocurred at column 1
> > DISPLAY error:  Invalid expression
> >   Expression = lst_day_cmg
> >
> >
> > Grads configuration as follows:
> > (Config: v1.9b4 32-bit little-endian readline
> > sdf/xdf
> > hdf-sds netcdf lats printim)
> >
> >
> > Below is the actual ctl file I am using:
> >
> > ***********************************************
> > dset ^MOD11C3.A2000061.004.2004116185101.hdf
> > dtype hdfsds
> > options yrev
> > undef 0s
> > unpack scale_factor add_off
> > xdef 7200 linear -180.0 0.05
> > ydef 3600 linear  -90.0 0.05
> > zdef 1 levels 1
> > tdef 1 linear 1jan1989 1dy
> > vars 16
> > LST_Day_CMG=>lst_day_cmg 1 z,y,x Monthly daytime
> > 3min
> > CMG Land-surface Temperature
> > QC_Day=>qc_day 0 y,x Sea surface temperature
> > Day_view_time=>day_view_time 0 y,x Sea surface
> > temperature
> > Day_view_angl=>day_view_angl 0 y,x Sea surface
> > temperature
> > Clear_sky_days=>clear_sky_days 0 y,x Sea surface
> > temperature
> > LST_Night_CMG=>lst_night_cmg 0 y,x Sea surface
> > temperature
> > QC_Night=>qc_night 0 y,x Sea surface temperature
> > Night_view_time=>night_view_time 0 y,x Sea surface
> > temperature
> > Night_view_angl=>night_view_angl 0 y,x Sea surface
> > temperature
> > Clear_sky_Night=>clear_sky_night 0 y,x Sea surface
> > temperature
> > Emis_20=>emis_20 0 y,x Sea surface temperature
> > Emis_22=>emis_22 0 y,x Sea surface temperature
> > Emis_23=>emis_23 0 y,x Sea surface temperature
> > Emis_29=>emis_29 0 y,x Sea surface temperature
> > Emis_31=>emis_31 0 y,x Sea surface temperature
> > Emis_32=>emis_32 0 y,x Sea surface temperature
> > endvars
> >
> > Thanks for your help,
> > Zhao
> >
> >
> >
> >
>
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>
>
> Brian Vant-Hull
> 917-318-4481
>
>
>
>
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