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[IDV #RTU-584517]: Example file with IDV gridded data issue

> IDV Folks,
> We are are the verge of converting several existing datasets from a previous 
> proprietary binary format into (hopefully) CF compliant netCDF to make the 
> data more accessible to the wider Earth science community.  Part of our 
> conversion process has been to test the new formatted data with the various 
> tools that support netCDF.  IDV is an obvious choice, and we ran into a 
> hiccup with that testing.  We have two main types of satellite data sets 
> across several different platforms: (1) a composite of each day's swaths, and 
> (2) a 3-day average of the same data.  The structure of both data sets is 
> nearly identical, with the exception that the daily composite (1) has an 
> array of "pass direction" flags, so each parameter has an ascending and 
> descending view.
> Both of these data sets (daily and 3-day) seem to be handled fine by other 
> tools, i.e. panoply, but we have a problem with the daily files when 
> attempting to read them with IDV.  IDV complains that it cannot find any 
> gridded data and (apparently) fails to open the file. Our best guess is that 
> the "pass direction" array is causing the problem, but based on our 
> interpretation of the documentation for both netCDF and IDV, the structure we 
> have created should be correct.
> We would like to get this resolved before starting the conversion of these 
> datasets at our repository - the Global Hydrology Resource Center (GHRC) - a 
> NASA DAAC.  We would really appreciate it if you could review the linked 
> files and give us a read on if we are doing something wrong or if this is a 
> problem for IDV.  If it is our problem, we would like to fix it before our 
> conversion effort.  If it is IDV's problem, then we can go ahead with our 
> conversion and hope it gets resolved.
> At the links below, is one example of both the daily composite and the 3-day 
> average.  We are using the Java netCDF 4 libraries to create these files, 
> which as we understand it generates netCDF-3 output.  A little confusing, but 
> that is what we understand from the documentation.
> Daily
> http://www.itsc.uah.edu/~keiser/projects/DISCOVER/netCDF/IDV_test/f13_20090101v7.nc
> 3-Day average
> http://www.itsc.uah.edu/~keiser/projects/DISCOVER/netCDF/IDV_test/f13_20090101v7_d3d.nc

Hi Ken,
    I checked these two datasets, the 3-day average is looking good in the IDV. 
The problem with the daily dataset is indeed this additional dimension. I don't 
think there is CF convention to deal with this type of dimension. But you do 
need a variable to go with a dimension. The only possible I can think about is 
to cheat this dimension as Ensemble, see the attached ncml file, and this can 
make this dataset being recognized as grid type in the CDM and can be loaded in 
the IDV. I will transfer this support to netcdf-java department to ask for 
their help.

> We appreciate any guidance you can provide on this.
> Ken Keiser
> ------------------------------
> Information Technology and Systems Center
> University of Alabama in Huntsville
> email: address@hidden
> phone: 256-824-6825

Ticket Details
Ticket ID: RTU-584517
Department: Support netCDF Java
Priority: Normal
Status: Open

Attachment: f13_20090101v7.ncml
Description: Binary data

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