Re: Resampling from lat/lon to projection


Kjell Røang wrote:

As mentioned elsewhere, we want to use another projections package ( ). We plan to use completly other kind out data
that we need to transform. I can't find this MapProjectionDisplay in my

You could still use GeoTools on the VisAD adapter by creating
a GeoToolsCoordinateSystem that would take a GeoTools object
and use that to do the conversion.  I'll look at GeoTools when
I get a chance (maybe next week).  MapProjectionDisplay
is in the examples directory.  The examples do not have
packages, so you would have to cd to the examples directory
and run java MapProjectionDisplay.

It sounds pretty much how I will like to do it, but I might use Ricks mods
to do the transformations. (JGrib should also support new projections as
many will use JGrib without using Visad). In VisAd notation, the data would
look something like:

time -> ((lat, lon, z?) -> (pressure, v-wind, u-wind, ...))

It would be good to support new projections.  As I say above,
if you are going to use GeoTools, then you could create a
GeoToolsCS that could be used in the VisAD objects (instead of
GRIBCoordinateSystem).  It would extend visad.georef.MapProjection.

I would also suggest that you try to do lazy evaluation of t
the GRIB file using FileFlatFields instead of FlatFields.  This
will be a little more work, but will only cause memory to be used
when a particular Field in requested.  So the structure would be:

time -> (((lat, lon, z) -> pressure),
         ((lat, lon, z) -> v-wind),
         ((lat, lon, z) -> u-wind),

The Vis5D and netCDF adapter (Plain) use this strategy.

Don Murray                               UCAR Unidata Program
dmurray@xxxxxxxxxxxxxxxx                        P.O. Box 3000
(303) 497-8628                              Boulder, CO 80307