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Re: Fwd: Data viewer



Martin,

your problem was discussed in today's THREDDS meeting. the best approach
would be for you to find an idl library for the Lambert Conformal
projection. someone mentioned that it's available but didn't know the
location, so some google searches should help out.

the projection info is in the netCDF file, it can be looked at using the
ncdump utility. ie for the wseta grid:

 model_id = 83 ;

 nav_model =
  "GRIB1" ;

 grid_type_code = 3 ;

 grid_type =
  "Lambert conformal projection" ;

 grid_name =
  " " ;

 grid_center = 7 ;

 grid_number =
  255 ;

 x_dim =
  "x" ;

 y_dim =
  "y" ;

 Nx = 149 ;

 Ny = 121 ;

 La1 = 36.972 ;

 Lo1 = -109.911 ;

 Lov = -105.5 ;

 Dx = 5439 ;

 Dy = 5439 ;

 ProjFlag = 0 ;

 Latin1 = 40 ;

 Latin2 = 40 ;

 SpLat = 0 ;

 SpLon = 0 ;

 ResCompFlag = 8 ;

The meaning of the above variables can be found at:

http://www.nco.ncep.noaa.gov/pmb/docs/on388/tabled.html

the lambert conformal grid is the 5th table on the page.


with the above info one should be able to calculate the desired lat/lon
points using the library.

robb...


>
>
>
> On Tue, 2 Nov 2004 10:41:38 -0800, Martin Landsfeld
> <address@hidden> wrote:
> > Hello Ben,
> > We are in the midst of developing data viewer and need a little help
> > with the ETA and WSETA data sets. We want to overlay the
> > two model outputs over each other but they are available in two similar
> > but different map projections. We need to have them in the same
> > projection
> > to accurately overlay them. We are able to retrieve the projection
> > parameters,
> > such as starting Lat/Lon, projection type, standard parallels, etc.,
> > but I
> > can not find any references on how to use these to calculate latitudes
> > and
> > longitudes for each data point. Are there lat/lon files available for
> > these
> > data sets? If not, is there a reference that you could send me that
> > would
> > provide the equations to calculate lat and lon at each point? The
> > projections
> > are both Lambert Conformal (conic) with the ETA National runs using
> > a standard parallel of 25 degrees N and the ETA Workstation runs using
> > a standard parallel of 40 degrees N. I have searched through the GRIB
> > documentation but I only find the parameter definitions and nothing
> > referring
> > to how they can be used to retrieve geospatial locations.
> > Any help is appreciated!
> > Thanks,
> > Marty Landsfeld
> >
> > The New Media Studio
> > www.NewMediaStudio.org
> > 805-966-1100
> >
> > On Sep 28, 2004, at 10:48 AM, Ben Domenico wrote:
> >
> > > Hi Bruce,
> > >
> > > As a talking point, I'll try to describe what we'd like to see
> > > delivered so you can think it over before the discussion.
> > >
> > > - Develop an equivalent of the data interactive publication:
> > >
> > > <http://my.unidata.ucar.edu/content/projects/THREDDS/DataPublications/
> > > SampeDataPublicationFor2005AMS.htm>
> > >
> > > using Macromedia Director and IDL instead of the Unidata IDV
> > > technology.
> > >
> > > - Implement the system in such a way that as many of the "Excercises"
> > > as possible can be accomplished with the Director/IDL version.
> > >
> > > - The Director/IDL version should be able to access the latest model
> > > runs using the THREDDS catalog entry.
> > >
> > > - Adequate documentation and consulting so that a sofware engineer
> > > familiar with Director and IDL can use the system to develop a similar
> > > data interactive document accessing datasets from a different THREDDS
> > > catalog.
> > >
> > > We can discuss and refine this during the phone call this afternoon.
> > > I just thought it would be good to have something to start the
> > > discussion.
> > >
> > > -- Ben
> > >
> > >
> > >
> > > --On Tuesday, September 28, 2004 9:16 AM -0700 Bruce Caron
> > > <address@hidden> wrote:
> > >
> > >> Hi Ben,
> > >>
> > >> talk to you this afternoon!
> > >>
> > >> bruce
> > >>
> > >>> Bruce,
> > >>>
> > >>> Tomorrow (Tuesday afternoon) 2 pm your time (3 pm Mountain time)
> > >> sounds
> > >>> good to me.   Looking forward to it.
> > >
> > >
> > >
> > >
> >
> >
>

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