[Paraview] [EXTERNAL] Paraview can't show grads origin data

[Moreland, Kenneth]

OK.  I see now.  Clearly I'm not familiar with the GrADS software or its
data formats.  If someone else on the ParaView mailing list is familiar
with GrADS it would be great if they speak up, but according to the mail
archives GrADS has not yet been discussed.


I suspect the problem is that ParaView simply does not know how to read
the type of netCDF files written by GrADS.  NetCDF is not a completely
specified file format.  Rather, it is a collection of arrays that are
"self describing."  That is, the arrays and dimensions are named and can
have properties, but to read them properly you really have to understand
what these metadata mean.

There are actually several readers in ParaView that use netCDF as the
underlying technology, but only one that makes an attempt to generally
read unknown "conventions."  It will assume that arrays are regular grids
with up to three physical dimensions (x/y/z or lat/lon/z) and optionally a
time dimension.  Based on about 5 minutes looking at the GrADS web pages,
I'm guessing that the netCDF file GrADS is outputting contains 5
dimensional arrays.  In this case, the ParaView reader won't know what to
do with 5 dimensions and will therefore issue an error if you try to read
one.  (You never actually said what went wrong, but perhaps that is it.)

I'm sorry that probably none of this is helping.  Ultimately, it sounds
like a new reader would have to be created for ParaView.

-Ken

On 3/13/12 2:28 AM, "wang" <wang at knmi.nl> wrote:

>Thanks for your reply.
>
>Grads is a software package that widely used by meteorological societies
>  worldwide. http://www.iges.org/grads/.
>The nc file I get can  be shown by ferret (which is also a software
>package
>used by earth science communities) and Grads (Grads can read binary and
>data).
>
>The problem may occurred by conversion...
>
>Xueli
>
>Moreland, Kenneth wrote:
>> I don't know what you mean by a "grad" or what problem it is causing, so
>> I'm going to make a total guess.  I am guessing that you mean gradian (a
>> unit equal to 9/10 of a degree).  Furthermore, because I can't think of
>> any other way such units would mess you up, I am guessing that you are
>> trying to write spherical coordinates in terms of gradians, but ParaView
>> is interpreting them either as degrees or as Cartesian coordinates.
>>
>>
>> Assuming that this is the problem, it is caused by the fact that the
>> default netCDF reader for ParaView honors the CF convention
>> (http://cf-pcmdi.llnl.gov), and the CF convention specifies spherical
>> coordinates in terms of degrees.  To specify angles in any other units
>>is
>> to break the convention.
>>
>> Your best solution is to convert your gradians to degrees (it's OK to
>>have
>> floating-point degrees) and write a netCDF file that properly follows
>>the
>> CF convention.
>>
>> If I have completely missed the point of your question, you'll have to
>> better explain what are grads and what problem you are having with them.
>>
>> -Ken
>>
>> On 3/12/12 10:13 AM, "wang"<wang at knmi.nl>  wrote:
>>
>>    
>>> Dear Paraview users,
>>>
>>> I have problem with data that origin of grads. We have a program to
>>> convert grads data into NetCDF format. But this data can not be shown
>>>in
>>> Paraview. I don't have any problem to show normal nc data.
>>>
>>> Have you ever experience the same problem?
>>>
>>> Thanks!
>>> Xueli
>>> _______________________________________________
>>> Powered by www.kitware.com
>>>
>>> Visit other Kitware open-source projects at
>>> http://www.kitware.com/opensource/opensource.html
>>>
>>> Please keep messages on-topic and check the ParaView Wiki at:
>>> http://paraview.org/Wiki/ParaView
>>>
>>> Follow this link to subscribe/unsubscribe:
>>> http://www.paraview.org/mailman/listinfo/paraview
>>>
>>>      
>>
>>    
>
>