<div dir="ltr">Hi James,<div><br></div><div>I converted the file to a netcdf via sdfwrite and you are right. The file opens almost instantly. I wonder why grib files are so slow to open and if this could be avoided? It is worth noting that the netcdf file is about 3x larger even with using the -zip option. Unfortunately since this is an archive, we can't just increase the data stored by a factor of 3. </div><div><br></div><div>I like your idea of the OPenDAP server, we may have to check into this if there is no other option. </div><div><br></div><div><br></div><div><br></div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Jan 14, 2016 at 4:05 PM, James T. Potemra <span dir="ltr"><<a href="mailto:jimp@hawaii.edu" target="_blank">jimp@hawaii.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
Hi Travis,<br>
<br>
This seems a little strange to me. I did a quick test with one of
our higher res data sets (global bathy) that is 21600 by 64800 (x,y)
and it loads almost instantly in GrADS. Of course generating a
display takes a long time, and my test was done on a netCDF file.<br>
<br>
This aside, could you run the data through an OPeNDAP server? Even
though it would be on the same machine, you could use the server to
subset via the DAP call, rather than relying on GrADS to load the
entire file.<br>
<br>
Jim<div><div class="h5"><br>
<br>
<div>On 1/14/16 12:54 PM, Travis Wilson -
NOAA Federal wrote:<br>
</div>
</div></div><blockquote type="cite"><div><div class="h5">
<div dir="ltr">
<p class="MsoNormal">Hi,</p>
<p class="MsoNormal"><br>
</p>
<p class="MsoNormal">At the NWS we have been using grads to
create images from grib files on the fly. Users use a front
end interface to select a model (which is just a grib file on
a server), field, and view, and submits a job. Within 3-4
seconds the server is able to launch grads, open the grib
file, and produce 50-100 images for the user to view. This
works extremely well for CONUS datasets with medium to coarse
resolutions (up to 6km). </p>
<p class="MsoNormal">We have started using higher resolution
grib files (1 km radar files are attached) and they are
substantially slower. The main problem comes from opening the
file. If a user selects radar for Northern California, it
takes grads approximately 18 seconds just to open the 1km
CONUS radar file (scanning descriptor file)..and then grads
plots rather quickly. </p>
<p class="MsoNormal"><br>
</p>
<p class="MsoNormal">A workaround we have been using is to
subset the data on the fly (since we don’t know the area the
user will select). This example regrids the CONUS radar for
northern California. </p>
<p class="MsoNormal"><br>
</p>
<p class="MsoNormal">wgrib2 1kmradar_201512241600.grib2
-small_grib 233:243 36.8:42.8
1kmradar_201512241600.grib2.small</p>
<p class="MsoNormal"><br>
</p>
<p class="MsoNormal">The small grib file will open in GrADS in
about 1 second. Regridding, and remaking the ctl and idx is
substantially faster, but still requires a lot of time. My
question is, is there any way to speed up the scanning of the
CONUS descriptor file without subset the grib file. For
example, grads would not scan the entire conus descriptor file
when we just need to look at Northern California (or whatever
portion of the US the users selects). </p>
<p class="MsoNormal"><br>
</p>
<p class="MsoNormal">We appreciate all the help,</p>
<p class="MsoNormal">Travis</p>
</div>
<br>
<fieldset></fieldset>
<br>
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