Re: MetApps ShapefileAdapter

Hi Don, Bill et al,

On the topic of projections/coordinate systems, I have a question (or
two!) about a coordinate system we would like to use.

The problem is basically how to handle the "dateline problem".

Currently we have an application which represents the entire world by
longitudes 0 to 360, using setRange(0.0, 360.0) on the scalar map of
Longitude. This is exactly the range that we want, but do not want to
use longitudes of 180 to 360 to represent the western hemishphere.

So effectively we want a range which goes from 0 to 180, then from -180
to 0 on one continuous display (ie dateline in the middle of the
display). So both the data and the display (ie labels) reflect this.

My impressions from the current discussion are that to achieve this we
would need:
1) to define a coordinate system which mapped the native data of (0 to
180; and -180 to 0) onto the (0 to 360) used by the display

2) and define a display side CS consistent with this 

3) maybe we might need to fiddle with other display characteristics to
ensure labels were consistent?

Am I on the right track? If so, I'd be grateful for an indication of how
much effort this might involve (ie day(s), week(s) or month(s)).

Thanks,

James


Don Murray wrote:
> 
> Luke-
> 
> "Luke A. Catania (TEC)" wrote:
> >
> > Is there a way to use a map projection with VisAD?   If so  there example
> > code?? After using the DisplayImplJ3D, I was able to get the map of the
> > world shape file displayed, but it does not look correct because of the lack
> > of a map projection.
> 
> As Bill mentioned, we use a Display side CS in MetApps.
> See ucar.unidata.view.geoloc.MapProjectionDisplay.  This
> will take either a visad.georef.MapProjection or a
> ucar.unidata.geoloc.Projection as input to set the background
> projection.  For a version of MapProjectionDisplay that
> uses vanilla VisAD (i.e. no Unidata classes), see:
> 
> ftp://ftp.unidata.ucar.edu/pub/dmurray/MapProjectionDisplay.java
> 
> This does not allow you to change projections, though whereas
> ucar.unidata.view.geoloc.MapProjectionDisplay does allow changes
> by creating a new DisplayRealTupleType with each change.
> 
> Don
> *************************************************************
> Don Murray                               UCAR Unidata Program
> dmurray@xxxxxxxxxxxxxxxx                        P.O. Box 3000
> (303) 497-8628                              Boulder, CO 80307
> http://www.unidata.ucar.edu/staff/donm
> *************************************************************

-- 
James Kelly                                          Regional Computing 
Phone: 61-3-9669-4724 Fax: 61-3-9669-4128     Email: J.Kelly@xxxxxxxxxx