Support UKV variable name change #364: Conditionally rename x,y dims …

[aouatefm]

Pull Request

Description

This PR adds backward compatibility support for UKV variable name changes (#364).

Problem: New UKV data uses different dimension names (x_osgb, y_osgb) while legacy data uses (x, y). The current code always renames x→x_osgb and y→y_osgb, which breaks with the new dataset.

Solution: Modified the open_ukv function to conditionally rename spatial coordinates only when legacy dimension names (x, y) are present. This maintains compatibility with both:

• Legacy data (renames x→x_osgb, y→y_osgb)
• New data (no renaming needed since dimensions are already x_osgb, y_osgb)

How Has This Been Tested?

• Tested with both legacy and new UKV dataset formats
• Verified spatial coordinates are properly handled in both cases
• Confirmed the function doesn't break existing workflows

If your changes affect data processing, have you plotted any changes? i.e. have you done a quick sanity check?

• Yes - verified data structure and coordinate naming in both scenarios

Checklist:

• My code follows OCF's coding style guidelines
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I have checked my code and corrected any misspellings