# [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 ucar.unidata.data.grid import GridUtil

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

Faculty of Geo-Information Science and Earth Observation (ITC)
University of Twente
Chamber of Commerce: 501305360000

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```

Attachment: MODIS2Dto3D.xidv
Description: MODIS2Dto3D.xidv

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