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[IDV #DFN-921227]: Obs Wind direction & speed to Streamline



Ah, you have point data. Ok, so first you will need to use the objective 
analysis capabilities of the IDV to put your data on a grid; The good news is 
that the gridded data can be found under the "Gridded Fields" derived 
quantities. You should be able to use the gridded fields to make the 
streamlines.

Cheers!

Sean

> Hi
> 
> Added User aliases but doesn't work.
> My obs data is point data in ASCII CSV file.
> Will it also support derived quantities in the "Gridded Fields"?
> 
> Eric
> 
> address@hidden> wrote:
> 
> > Greetings Eric,
> >
> >
> > > Hi
> > >
> > > Currently, I have obs wind direction (in degree) and speed (m/sec) data
> > and
> > > which can be used to draw wind barb in IDV.
> > >
> > > Question 1:
> > >
> > > I want to use same set of data to draw the streamlines.  I tried to put
> > > the direction and speed into Formulas > Grids > Make flow vectors from
> > > u and v data.  But it cannot produce any streamlines.  Should I convert
> > > the direction and speed into u and v by myself or any simple way to do
> > it?
> >
> > If the IDV understands you variables to be speed / dir, then the option to
> > make flow vectors from speed / dir should automatically show up under
> > 'derived quantities' in the field selector (you should not need to
> > explicitly use a formula). Since the IDV isn't recognizing your speed / dir
> > variables, you need to add their names to the aliases for SPEED and DIR.
> > From the top toolbar in the IDV, click "Tools" -> "Parameter Alias Editor."
> > When the editor pops up, click the tab for "System aliases" and find SPEED
> > and DIR under the column "Name". If you double click either of those, a box
> > will pop up that will allow you to add your variable name to the alias list.
> > Do that for both SPEED and DIR and see if that works. Once you add them,
> > they will show up on the "User aliases" tab. If you ever need to add more
> > aliases for SPEED or DIR, just go through the steps above, but use the
> > entries listed under the "Users aliases" tab, not "System aliases."
> >
> >
> > >
> > > Question 2:
> > >
> > > And I noticed that the streamlines output from IDV is quite different
> > > from NCL..  The spacing between two streamlines in NCL are more even
> > > which make NCL streamlines look more evenly distributed.  Can I get a
> > > more evenly distributed streamlines from IDV?
> >
> > Streamlines can be tricky. However, if you have streamlines plotted you can
> > go to the Dashboard and under the "Displays" tab (with your streamline field
> > selected), you can manipulate the behavior of the streamlines. In
> > particular, you may want to play with the Streamline density, skipping a
> > certain number of point in the X and Y grid space, or using a smoothing
> > function.
> >
> > Cheers!
> >
> > Sean
> >
> > >
> > > Thanks a lot. Look forwards to your reply.
> > >
> > > --
> > > Best Regards,
> > > Eric Fong
> > >
> > >
> >
> >
> > Ticket Details
> > ===================
> > Ticket ID: DFN-921227
> > Department: Support IDV
> > Priority: Normal
> > Status: Closed
> >
> >
> 
> 
> --
> Best Regards,
> Eric Fong
> 
> 


Ticket Details
===================
Ticket ID: DFN-921227
Department: Support IDV
Priority: Normal
Status: Open


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