RE: Grid projection scheme problem

• To: "Latimer, S" <s.latimer@xxxxxxx>
• Subject: RE: Grid projection scheme problem
• From: Robb Kambic <rkambic@xxxxxxxxxxxxxxxx>
• Date: Thu, 17 Feb 2005 16:41:57 -0700 (MST)

On Thu, 17 Feb 2005, Latimer, S wrote:

> Robb,
>
>      Thanks for your help....
>      There exists a few problems with attempting to extract data by putting 
> the cursor over a point: 1) we are not sure what the lat/lon is at that 
> point, 2) since I need the u,v components at 17 discrete points and 4 
> levels--this operation would result in a prodigious amount of time 
> consumption, and 3) the projection scheme used in the model as projected on 
> the IDV screen does not have equally spaced grid points which raises 
> questions about whether the lat/lon we type in is the actual lat/lon location 
> on the map (this issue confuses me the most).
>       I looked at the GIS software link you gave me.  Do you know if the type 
> of files I have would enable me to extract the u,v component given the 
> lat/lon?  It did not look like the type of files I have would be compatible 
> for importing...
>       I know this is a difficult problem that is probably not easily solved 
> and I thank you for all of your help.  Any  suggestions or referrals to 
> others about this problem would be greatly appreciated.  Thanks again,

Stephen,

at this point i'm out of suggestions but i do know the myWorld program
does handle netCDF files. but will the program allow you to extract the
data that you are requesting, don't know.  you could write a support
question to them with your request.

robb...


>
> Stephen Latimer
> Meteorology Graduate Student
> Texas Tech University ATMO
> Lubbock, TX 79409
>
> ________________________________
>
> From: Robb Kambic [mailto:rkambic@xxxxxxxxxxxxxxxxxxxxxxxx]
> Sent: Thu 2/17/2005 16:55
> To: Latimer, S
> Cc: decoders
> Subject: Re: Grid projection scheme problem
>
>
>
> On Wed, 16 Feb 2005, Latimer, S wrote:
>
> > Robb,
> >
> >     Thanks for all of your help.  The netCDF converter works very well.
> >     I now have a problem with extracting the data in the netCDF format.  We 
> > (my advisor and I) tried to access the netCDF model file using IDV and it 
> > displays fine.  The only problem is that I am attempting to obtain u,v wind 
> > components at several levels above discrete points (i.e. lat, lon).  The 
> > hope is that if we resolve the projection scheme (Lambert Conformal) we 
> > would be able to automatically extract the data by use of Matlab.
> >     We have tried to look at various equations in Holton (not helpful)  and 
> > other sources (Penn. state, somewhat helpful) that in essence describe 
> > variables like true latitude, longitude, etc. with several complex 
> > equations describing how a grid point is located on the map at a particular 
> > location.  My advisor also tried something called the "Great Circle 
> > calculator" (method found at this website 
> > http://www.meridianworlddata.com/Distance-Calculation.asp   ) and found 
> > that the grid does not appear to have a "regular grid spacing" in terms of 
> > distance, nor does it appear to be laid out using a perfect "E-W" 
> > orientation.
> >     Do you know (or know someone who might) what or how we can possibly 
> > extract from discrete points the u, v wind components from several levels 
> > data, given this problem or issue?
>
> Stephen,
>
> that's a tough question.  the idv does the conversions at a lower level
> so you really don't have access to the routines to request values of
> particular lat/lon locations.  when you display the data, can't you get the
> values over particular lat/lon location by placing the cursor over the
> location?  if it's more than a few points, this would be hard.  there is a
> s/w package called MyWorld that may help you, url:
>
> http://www.worldwatcher.northwestern.edu/myworld/
>
>
> robb...
>
> >    Thanks again for your help.
> >
> > Stephen Latimer
> > Meteorology Graduate Student
> > Texas Tech University ATMO
> > Lubbock, TX 79409
> >

==============================================================================
Robb Kambic                                Unidata Program Center
Software Engineer III                      Univ. Corp for Atmospheric Research
rkambic@xxxxxxxxxxxxxxxx                   WWW: http://www.unidata.ucar.edu/
==============================================================================