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[IDV #XVT-855811]: IDv problems

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  • Subject: [IDV #XVT-855811]: IDv problems
  • Date: Tue, 16 Oct 2007 14:06:13 -0600
Hi Bill-

> OK.  I played around a bit with the tutorial you suggested.  I learned a
> lot - wish I had looked at it earlier (not sure I knew much about it
> earlier).

Glad that helped you out.

> We did have another question -- I went to some thredds site to get
> satellite data and was able to display the 4 km image fine (which covered
> the E US and Atlantic and part of Africa).  However, the 1 km image failed
> - seemed to run out of memory.  So, we upped the memory as you suggested
> to 1GB.  Even doing that, the 1 km data still failed to come up (you could
> watch it gradually hog all that memory).  Is there some specific memory
> amount that it is well-known is needed to handle the 1 km data?  Daryl
> mentioned that garp handles 1 km data without a problem, so we were
> suprised that we couldn't get IDV to work even with 1 GB of memory.


Garp uses the X-Server to subset the data so it doesn't display all
the pixels.  The IDV displays  all the pixels of a 1km image and
has to convert each  pixel to 4 bytes.  Plus, satellite images 
(texture maps) are a resource hog, so it is best to subset the images
before displaying them.  I would also suggest not using a THREDDS
server for satellite imagery because the interface for these GINI
images is not well tested and you can't aggregate on time.  Better
to use the Image Chooser and select one of the GINIEAST, GINIWEST or
GINICOMP datasets.  That chooser allows you to subset over a region
which is typically how you want to look at the 1km imagery anyway.

You can also set the max image size in the Edit->Preferences dialog
under the Formats&Data tab.  So, if you set it to 1000000 pixels,
the IDV will set the skip factor in the control accordingly so the
image will be subset before display.  Note that there is no areal
subsetting on display, only when you load the data.

There's a section in the User's Guide on performance tuning at:

http://www.unidata.ucar.edu/software/idv/docs/userguide/misc/PerformanceTuning.html

Don

Ticket Details
===================
Ticket ID: XVT-855811
Department: Support IDV
Priority: Normal
Status: Open