[gradsusr] GrADS vs GDS data discrepancies

[Jennifer M Adams]

Matt,
The problem with undef values is likely related to this note on the GDS home page:

"The release of GrADS version 2.0.a6 implemented some necessary changes related to the handling of undefined values. These changes can affect the GDS. If you are administering a GDS version 2.0 with GrADS 2.0.a6 or higher behind it, then a 1-line patch is needed for the file $GDSHOME/scripts/subset.gs. The patched version is here<http://cola.gmu.edu/grads/gds/patched_subset.gs>. Updating the subset.gs script does not require a reinstallation or even a reload of your GDS."

You should be using a newer version of GrADS anyway … why 2.0.2 ???

As for the seg fault, it’s impossible to diagnose without knowing more about your data file. Try comparing the ncdump output on your native file and the GDS URL and see where they differ.
—Jennifer

On Feb 11, 2017, at 3:18 PM, Matt Alonso <matt.alonso at GMAIL.COM<mailto:matt.alonso at GMAIL.COM>> wrote:

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.

Background:
- 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">
      </dataset>

- 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:

1)

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.

2)

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!

Regards,
Matt
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--
Jennifer Miletta Adams
Center for Ocean-Land-Atmosphere Studies (COLA)
George Mason University



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