# Re: Creating a new vertical domain

```Hi Bill-

Bill Hibbard wrote:

```
```Well, theta doesn't always increase with decreasing pressure.
Even where it does, the grid boxes may be so distorted that
the Gridded3DSet constructor rejects them.
```
```
That's what seems to be happening.

```
```If your (lat, lon, press) doesn't have a reference, then
it can be a reference for a CS to (lat, lon, theta) and
you can resample your (((lat,lon,theta) -> altitude) Field
to a grid defined in (lat, lon, theta). But of course
defining the CS requires you to invert the
((lat,lon,press) -> theta) to a ((lat, lon, theta) -> press).
```
```
Actually, my field domain is:

(x,y,press) with a CS to (lat,lon,alt)

What I tried was taking the (x,y,press) -> theta and making
an EmpiricalCS from (x,y,press) to (lat,lon, theta) (replacing
alt values with theta) and then tried resampling.  That all worked
until I tried to display it where I get some
"reduce_inner failed" errors.

```
```As a last resort, you can do a 1-D computation along the
vertical line above each (lat, lon) grid point, interpolating
altitude values for each of your theta levels. If there are
no theta "inversions", you might be able to do this with
resample() calls on a bunch of derived 1-D Fields.
```
```
My main goal here is to display fields along a constant
theta surface.  Ignoring the inversions and other theta issues
that you and Tom described, here's something that worked that is
sort of what I'm trying to do:

If I create a FlatField of (lat,lon,press) -> (theta, Z, (u,v))
and display it in a spreadsheet cell (Omni control in IDV) with
mappings:

lat -> YAxis
lon -> XAxis
Z -> ZAxis
theta -> SelectRange
u -> Flow1X
v -> Flow1Y

and make a very narrow range of the select for theta (e.g. 309-311K), I
basically get a display of wind vectors on an ~310K isentropic surface.

To do this in the main IDV window, I need a domain with a vertical
reference of Z and be able to slice along a constant theta value.

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
"Time makes everyone interesting, even YOU!"
*************************************************************

```
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