Vector rotation for grids where the "intrinsic" and "extrinsic" coordinate system are different about oceananigans.jl HOT 8 OPEN

Extrinsic is what we decide. When we use the cubed sphere we want to use geographic coordinates.

But vector fields on the c-grid have their own coordinate system dictated by the structure of the grid. Except for LatitudeLongitudeGrid, the geographic coordinate system does not coincide with the "other" coordinate system (I called it intrinsic above, but if this is confusion we need another name) that's associated with the grid.

What language would you like to use to describe (1) the coordinate system that we would like to impose on the grid for the user interface and 2) the coordinate system that the raw vector fields use (I'm trying to avoid the language I proposed to ask this question).

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OK, I think I understand the issue mentioned here but the terminology intrinsic and extrinsic is not self-explanatory (for my intuition at least).

I'm not trying to argue against the names, I just want to understand exactly what's been discussed.

I think something in this spirit @siddharthabishnu bumped into in trying to set initial conditions or surface forcing on a ConformalCubedSphereGrid..?

from oceananigans.jl.

OK gotcha.

As I said, I didn't want to trigger a naming discussion. But I just wanted to ensure that I understand what's discussed. I understand now! Thanks!

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Well I think we want self-explanatory names though. So please let us improve the names if they are not self-explanatory.

from oceananigans.jl.

I think this concept is hard to be encapsulated in two words -- let me think though!

from oceananigans.jl.

Here was our original thinking:

intrinsic means: "belonging to a thing by its very nature"

so, the coordinate system that is "intrinsic" to the grid is associated with the grid's structure.

The oppposing word to "intrinsic" is extrinsic: "originating from or on the outside". This indicates that the extrinsic coordinate system is a choice imposed on the grid, ie we decide.

What do these words mean to you?

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The words do actually mean that for me as well, i.e. "belonging to a thing by its very nature" or "originating from the outside".

But because I've never before heard them in the context of coordinate systems it was not totally obvious to me what their meaning in this context was from just by seeing the name. But it did became clear soon!

I think it's ok that some of the names aren't 100% self explanatory just by reading the name and you need to read a bit the docstring or something to understand 100% what these objects/methods are.

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Oh true, but I think the problem is that when I say "the extrinsic coordinate system for the Tripolar grid is geographic coordinates", that this doesn't make sense. We need that to make sense...

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