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[IDV #BWV-959430]: export grid data is incorrect

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  • Subject: [IDV #BWV-959430]: export grid data is incorrect
  • Date: Sat, 05 May 2012 05:31:18 -0600
Greetings Tom,

My guess is that it has something to do with the fact that the number of 
longitude values (720) isn't nicely divisible into the range of longitude 
(359.5 degrees). If longitude went from -180 to 180, then there would be a 
clean 0.5 degree delta_lon, so to say. However, the delta_lon for the range 
359.5 degrees is something like 0.499305(rep); if this gets rounded up to 0.5, 
then you end up with values at 180.25 degrees.


That said, It would be most helpful to get the original netcdf file to figure 
out where things go wrong. The best method to get us a sample would be to 
upload it to our RAMADDA repository:

http://motherlode.ucar.edu/repository/entry/show/RAMADDA/Unidata/Software/IDV/Support+Uploads/

Cheers!

Sean

> Hi, using IDV 3.0, I exported a gridded variable from netcdf to an Excel 
> file. Here is a snippet of the netcdf header for variable t_ref_bulk:
> 
> dimensions:
> lon = 720 ;
> lat = 360 ;
> 
> variables:
> 
> double lon(lon) ;
> lon:long_name = "longitude coordinate" ;
> lon:standard_name = "longitude" ;
> lon:units = "degrees_east" ;
> 
> double lat(lat) ;
> lat:long_name = "latitude coordinate" ;
> lat:standard_name = "latitude" ;
> lat:units = "degrees_north" ;
> 
> float t_ref_bulk(lat, lon) ;
> t_ref_bulk:long_name = "Topsoil Reference Bulk Density" ;
> t_ref_bulk:units = "kg/dm3" ;
> t_ref_bulk:missing_value = -999.f ;
> t_ref_bulk:grid_mapping = "crs" ;
> 
> The range of lon = { -179.75, 179.75 }
> 
> The exported values of each var has 32 values at lon = 180.25. e.g.,
> 
> lon, lat, value = 180.25, 71.25, 1.470
> 
> The issue is that there is no value of lon == 180.25.
> 
> If you need the original netcdf file for debugging, I can arrange to get it 
> to you.
> 
> --
> 
> Tom Hilinski
> Natural Resource Ecology Laboratory
> Colorado State University


Ticket Details
===================
Ticket ID: BWV-959430
Department: Support IDV
Priority: Normal
Status: Open