Some difficulties asigning "mesh" and other small issues with layered 2D

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Jun 29, 2015, 6:25:46 PM6/29/15

Hi all,

This is kind of a dual post since I left something on GitHub ... is issue tracking getting watched? Is it a good place for discussion?

My troubles start when I want to assign my_var:mesh for data defined on a layered 2D mesh. This seems trivial for the example in the specification, which is Mesh2_waterlevel, because it is a 2D quantity. However, it seems to me that a layered 2D mesh is what Bill Howe would call "the cross-product of an unstructured mesh in the horizontal with a structured mesh in the vertical". As far as I can tell, the standard simply shows how these two parts are constructed independently. It doesn't unite them so that I can refer to it by name.

In practice, Mesh2 is just a regular ol' 2D mesh unless you search for the Mesh2_layers to find out it is more than that. There is a temptation for both 2D and 3D data holders to reference Mesh2D as their "mesh". There is some economy to re-use of the 2D mesh, and it helps to avoid inconsistency, but the same mesh can't be used for two different data structures with different dims. It also belies the over-simplicity of the earlier discussion of whether there should be a prescribed variable order because now there is more than one mesh and how do you order those? My apologies if I've missed something. This seems like a common use case.

Also, in ours and many other vertical coordinate systems (Z, SZ hybrid) the number of layers will vary in shallow and deep fluids. The vertical dimension is going to be a maximum number of layers, similar to what CF would call an incomplete multidimensional array representation (
Is there a place in the UGRID standard to flag the first in-domain layer in the water column for each node or volume? This to me is distinct from being physically wet/dry at the moment, and at least in our model it is a permanent choice.

Thanks for any guidance you can give,


Chris Barker

Jun 29, 2015, 7:18:37 PM6/29/15
to esatel, UGRID Interoperability
On Mon, Jun 29, 2015 at 3:25 PM, esatel <> wrote:

This is kind of a dual post since I left something on GitHub ... is issue tracking getting watched? Is it a good place for discussion?

I think we should capture discussion like this on the gitHub project -- better documentation of the process.

But good idea to post to the list to get it going -- I don't seem to following the gitHub issues, for instance.

I'll post there:


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Christopher Barker, Ph.D.

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