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[IDV #COD-764409]: GrADS ctl with Height (in km) as vertical scale

Hi Stefan-

> GrADS is able to open up the ctl/dat pair just fine using height coordinates. 
> ZDEF can be either in height or pressure for GrADS ctl files, even though it 
> typically is in pressure. I think the IDV sees the ctl file having ZDEF as 
> only having pressure as the only possible vertical coordinate, while it is 
> possible it can contain heights. So, is there anyway to add this possibility 
> into how the IDV opens up GrADS ctl files?

As you note there is nothing in the Grads Data Descriptor File (e.g. ctl file) 
that specifies the unit of the vertical dimension.  When I wrote the GrADS 
IOSP, I ran into 3 types of vertical level units - hPa, Pa and none (just a 
level number).  The default is hPa, but if there are values > 1050, I switch to 
Pa.

Since GrADS is pretty loosey goosey about what can go in a ctl file, one thing 
we could do is use the attribute metadata 
(http://www.iges.org/grads/gadoc/descriptorfile.html#ATTR) to specify the units 
of the vertical dimension like so:

@ zdef String units meter

What do you think about this?

Could you upload you file to the IDV uploads area so I can have something to 
test with?  It will probably take a while before this can get into the IDV, but 
I'll try to work on it when I get a chance.

Don Murray


> On Feb 22, 2012, at 11:49 AM, Unidata IDV Support wrote:
> 
> > Hi Stefan.
> >
> > First off, sorry for the delayed response. We have been attending 
> > conferences and giving workshops.
> >
> > We believe the GrADS spec is not being adhered to. As far as we can tell, 
> > GrADS expects levels to be defined as pressure (not KMs). We don't think 
> > the IDV can help here until the ctl and data file are fixed.
> >
> > Best,
> >
> > Unidata IDV Support
> >
> >
> >> Full Name: Stefan Cecelski
> >> Email Address: address@hidden
> >> Organization: University of Maryland
> >> Package Version: 3.0u2 build date:2012-02-08 08:06 UTC
> >> Operating System: Mac OS X
> >> Hardware: Java: home: 
> >> /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home version: 
> >> 1.6.0_29 j3d:1.5.2 fcs (build4)
> >> Description of problem: Hi all,
> >>
> >> I recently converted my wrf output to height levels via ARWpost to create 
> >> a grads ctl/dat pair. When I open the ctl file (attached) in IDV, the 
> >> vertical levels are automatically presumed as pressure levels, even though 
> >> the levels are height above ground in km. Is there anyway to trick the IDV 
> >> in to seeing the levels as height levels instead of pressure levels?  The 
> >> advantage of using height levels is evenly spaced vertical cross-sections 
> >> via a transect view. However, since the IDV sees the levels as pressure 
> >> levels, all the data is not viewable in the traditional transect view 
> >> display because the pressures are all between 0 and 20 hPa! Thanks for any 
> >> advice you might have.
> >>
> >> V/R,
> >>
> >> Stefan
> >>
> >>
> >
> >
> > Ticket Details
> > ===================
> > Ticket ID: COD-764409
> > Department: Support IDV
> > Priority: Normal
> > Status: Closed
> >
> 
> 
> 


Ticket Details
===================
Ticket ID: COD-764409
Department: Support IDV
Priority: Normal
Status: Open