[gradsusr] GrADS vs GDS data discrepancies

Matt Alonso matt.alonso at gmail.com
Sat Feb 11 15:18:55 EST 2017

Hi all,

Long time user of GrADS but first time user of GDS.  When attempting to
plot the same dataset locally vs going through GDS, I am running into some
strange behavior.

- same CentOS 6 machine is being used to run GrADS and GDS
- GrADS v2.0.2 binaries
- GDS 2.0
- data is netcdf but I am using a ctl file for templating purposes
- dataset entry in GDS xml file:

      <dataset name = "grid_hist"
               file = "/path/to/data.ctl"
               url = "http://www.iges.org/grads/gds/"
           format = "nc">

- the ctl file in the dataset path (above) is (literally) the exact same
path used when I mention the "local dataset"
- each netcdf file is ~65MB

Two issues:


When opening the data via GDS, GrADS does not appear to identify
undefined/missing values.  The undef value in the ctl and netcdf file is
-999.0.  When using "set gxout stat" on the local dataset for an arbitrary
domain and variable, it shows an Undef count > 0 and a Min of 0, but the
GDS file shows Undef count = 0 and a Min = Undef value.


When I open either the GDS or local data set, the lon/lat extent printed is:

LON set to -180 179.945
LAT set to -90 89.9725

If I do not change any of the dimensions and try to display any metric in
the file - using any gxout - the local dataset opens fine, however, using
the data in GDS causes GrADS to segfault.  There are no errors in gds.log,
it even shows "success" in the FINISHED record.

If I DO change the lat/lon to be any subset of the entire domain, then both
the local and GDS datasets plot fine - ignoring the behavior in #1 above.

I am sure I am doing something wrong but do not seem to be able to figure
out what.  Thanks in advance for your help!

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