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Check SGRID node dimensions and coordinates against the dataset - #3035
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Add ds.sgrid.assert_metadata_ds_consistency() which, in addition to the existing face/node size check, asserts that: - node_dimensions coordinate variables have axis attributes X then Y - node_coordinates exist, are defined on the node dimensions (1D coords along their own axis), and have longitude/latitude units in X then Y order when in degrees SGridDatasetInconsistency now subclasses ValueError. Also fix croco_to_sgrid node_dimensions (xi_rho, eta_rho), and update the example datasets to use per-axis degree units and to define node dimension coordinates in the sgrid_dataset strategy.
VeckoTheGecko
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Nov 4, 2026
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Some changes to the test suite/data generation was needed to attach this new metadata. There is also a change to convert.croco_to_sgrid.
There's no change to the docs - everything works like before.
| max_lat = 90.0 if mesh_str == "spherical" else 1e6 | ||
| unit = "degrees" if mesh_str == "spherical" else "m" | ||
| x_unit = "degrees_east" if mesh_str == "spherical" else "m" | ||
| y_unit = "degrees_north" if mesh_str == "spherical" else "m" |
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This change isn't strictly necessary, but I think it being more explicit is nice
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| # A 1D node coordinate (i.e., a rectilinear grid) must lie along its own axis. If one of the node | ||
| # dimensions has been indexed away (e.g., via isel) a 2D coordinate can legitimately be 1D along the other | ||
| if both_node_dims_in_ds and da.ndim == 1 and da.dims != (node_dim,): | ||
| raise SGridDatasetInconsistency( | ||
| f"Node coordinate {coord!r} is 1D with dims {da.dims}, but as entry {expected_axis!r} in " | ||
| f"node_coordinates={metadata.node_coordinates!r} it is expected to be defined on node dimension {node_dim!r}. " | ||
| f'HINT: Make sure node_coordinates in the SGRID metadata is ordered as "X" then "Y".' | ||
| ) |
| ) | ||
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| def _assert_node_coordinates_well_defined(ds: xr.Dataset, metadata: SGrid2DMetadata): |
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I think this function is the main thing worth reviewing @erikvansebille
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Looks very good - thanks for adding this code to check the SGrid consistency!
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Description
There was some existing tooling for checking that SGRID metadata was consistent with the underlying dataset (this logic was in a function
assert_metadata_ds_consistency). This consistency check was limited to the padding time and number of observations along dimensions (i.e., a padding of None means that there is one less edge than nodes, etc.).This PR extends the consistency checks to also ensure:
This PR also makes the function
assert_metadata_ds_consistencya method on the accessor, making it more accesible to the rest of the code.minor changes
SGridDatasetInconsistency now subclasses ValueError.
Also fix croco_to_sgrid node_dimensions (xi_rho, eta_rho), and update the example datasets to use per-axis degree units and to define node dimension coordinates in the sgrid_dataset strategy.
Checklist
mainfor normal development,v3-supportfor v3 support)AI Disclosure