Re: Problems with polar-stereographic 3d files

Hi Heiko-

Your post is timely as I'm looking into this issue today.

Heiko Klein wrote:
I've been using IDV for a while to display 2d fields in a polar-stereographic grid (CF convention). Now I tried to see a 3d field with sigma levels. Though the projection parameters are the same, when looking at a plan-view of a single layer, idv reverts to its default projection instead of my polar-stereographic view.

The problem is that for the IDV to plot the 3D sigma levels
in the map display, it needs to have a relationship between sigma
and altitude.  The only way we have to do this is transform the
grid to altitude values and in the process the projection information
gets lost.

When I try to make a vertical cross-section, I cannot see any data. The altitude display shows always a 'Distance along transect' scale from -0.4km .. 0.4 km and no altitude scale at all (autoscale y axis). The location coordinates of the cross-section are updated correctly.

This was reported last week by another user. It uncovered
a bug in the underlying netCDF Java library which has been fixed, so
now I have to see what's happening on the IDV side.

This looks all like a problem with my projection in the 3d fields, but I couldn't find any mistakes. Maybe somebody else can look at it? The file can be downloaded at

I hope to have this figured out today, but since it involves a radical
change in how we deal with the sigma grids, it might have other reprecussions.

Don Murray                               UCAR Unidata Program
dmurray@xxxxxxxxxxxxxxxx                        P.O. Box 3000
(303) 497-8628                              Boulder, CO 80307