Using the visad/examples/MapProjectionDisplay as a template, I have
learned how to do map projections is VisAD. My preferred projection
classes are the ones from IDV, i.e. ucar.unidata.geoloc.projection.*,
with the ucar.visad.ProjectionCoordinateSystem the bridge to the visad
classes.
Now I'd like to change map projections within a display, say from a
Lambert to a Mercator. Trying this, I first remove scalar maps for
RealType.Latitude and RealType.Longitude from my DisplayImpl (J2D). But
then when I try to build a new DisplayTupleType with DisplayRealTypes
from the example visad app, I get errors. Seems like a DisplayRealType
must be uniquely named. To get around this, I just make sure that the
N'th time I set the display coord sys, I name the DisplayRealType with N
in the name. I did think about just catching the TypeException and
continuing regardless but was unsure of the ramifications.
I also tried keeping the display real types and just building a new
tuple type for each map projection, but that failed with a 'display real
type already in a tuple' error.
Can anyone explain why such types must be uniquely named? On a related
note, is it a waste to be building 3 display real types and a
displaytupletype every time I want a new display side coordinate system,
i.e. a new map projection?? Is there a better way to achieve my goal.
I note that what I really want is a setCoordinateSystem on my
DisplayTupleType, then I wouldn't even have to remove the scalar maps at
all (??)
Hmm, it's just dawned on me that IDV allows in-display map projections
on the fly, can anyone enlighten me there?
Any help appreciated.
Stuart
