[visad] construct a 3D grid from multiple 2D grids

Hi,

In Unidata's GridUtil package there is a method to slice a 3D grid to
obtain a 2D fieldimpl.

Now, I basically want the reverse: construct a 3D grid from many 2D grids
with similar coordinate systems.

Attached 20 discrete (MODIS) vertical levels (nlevs=20) corresponding to
the following pressure-levels (in mb):
5,  10,  20,  30,  50,  70,  100 , 150 ,  200 , 250 ,  300 ,   400  ,
500 , 620 ,  700 ,   780 ,  850 ,  920 ,  950, 1000

For each level there is the retrieved temperature field and a geopotential
height field.

So the idea is to take each temperature field and resample the
geopotential height field at each x,y,z point to end up with a field
temperature at pressure point (assuming a standard atmosphere).
This can be done, but the solution is not straight forward. As I have
limited understanding of the VisAD data model, could you help me in the
right direction?

Attached an IDV-bundle containing the input 2D grid, and below this
message a _very_ ugly attempt to get this going.

Cheers, Tyn


def makeMODISSwathTo3DSet(a,b):
  from visad import FunctionType, FieldImpl, Gridded3DDoubleSet, Set, Unit
  from visad import RealType
  from visad import RealTupleType
  from visad import Gridded3DSet
  from visad import CartesianProductCoordinateSystem

  from ucar.unidata.data.grid import GridUtil
  import ucar.visad.quantities.AirPressure as ap

  timedom = a.getDomainSet()
  numTimes = timedom.getLength()

  dom1 = GridUtil.getSpatialDomain(a)
  xyCs = dom1.getCoordinateSystem()

  samples = dom1.getSamples(0)
  zCs = ap.getStandardAtmosphereCS()
  #print zCs
  print zCs.getLengths()
  newCS = CartesianProductCoordinateSystem(xyCs, zCs)
  
  sdomain = Gridded3DSet(RealTupleType.SpatialEarth3DTuple, samples,
                        dom1.getX().getLength(), dom1.getY().getLength(),
                        None,
                        None,
                        dom1.getSetErrors(), 0, 0)

  image = GridUtil.setSpatialDomain(a,sdomain)
  newTime = Gridded3DDoubleSet(RealType.Time, timedom.getSamples(0),
                               numTimes,
                               timedom.getCoordinateSystem(),
                               timedom.getSetUnits(),
                               timedom.getSetErrors(), 0)
  newType = FunctionType(RealTupleType.Time1DTuple, image[0].getType())
  timeImage = FieldImpl(newType, newTime)
  for i in range(numTimes):
    timeImage.setSample(i, image[i],0)
  return timeImage




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Attachment: MODIS2Dto3D.xidv
Description: MODIS2Dto3D.xidv