The reason I want to do the transformations (projections) ourself, is to be
able to support more output projections (to the user). We will probably use
the projection package in geotools. The interpolation we gladly let VisAd
If 'geotools' can convert an array of points from one projection to
another, you could create a VisAD CoordinateSystem that simply
interfaces with that.
The JGrib package now handles Lambert and Stereographics grids and convert
it to lat/long. Probably we will be able to support more coordinate systems
in the future. (JGrib is an open source project at
I would like to continue to expand the projections that are supported in
GRIBCooridnateSystem, especially when it comes to the "grid number" ones
- right now it only knows about 201,202,203,211,212,215,236.
Another question related to interpolation: If one wants to interpolate to a
pixel sized grid, is it more efficient to first interpolate to a "coarse"
rectangular grid (both geometry and topology) and from there interpolate to
the pixel sized grid?
If the reason you want to interpolate to a "pixel sized grid" is to be
able to show a grid as an image, then I would suggest just letting VisAD
do the display using your coarse grid. If there is some other reason,
I'd be curious to know...?
I would avoid a double interpolation for the reason that you would be
essentially filtering your data twice and might introduce side effects
that are unpleasant. It certainly could be more computationally
efficient to initially interpolate to every N-th point in your "pixel
grid" and then do a linear interpolation in between these points...but
it does beg the question about why you'd like to use a 'pixel sized
grid' in the first place.
Tom Whittaker (tomw@xxxxxxxxxxxxx)
University of Wisconsin-Madison
Space Science and Engineering Center
Cooperative Institute for Meteorological Satellite Studies