[convert] Ensure winding order of polygon linear rings#28
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[convert] Ensure winding order of polygon linear rings#28
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BenjaminPelletier
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Mar 12, 2026
| type="Polygon", | ||
| coordinates=hp.coordinates if "coordinates" in hp else None, | ||
| coordinates=ensure_polygon_rings_winding_order(hp.coordinates) | ||
| if "coordinates" in hp and hp.coordinates is not None |
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Will this work if hp.coordinates is []? (seems like it might crash) Perhaps:
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| if "coordinates" in hp and hp.coordinates is not None | |
| if "coordinates" in hp and hp.coordinates |
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Fix focagis/geoawareness-cis#8
Issue: linear rings of some polygons in the original ed269 do not respect the right-hand rule as specified by https://datatracker.ietf.org/doc/rfc7946/ section 3.1.6.
With the changes in this PR we ensure that the winding order do respect this rule.
We do so by using the Shoelace formula to determine whether the coordinates are specified clockwise or counter-clockwise, and reverse them if that is necessary.
The output of the converter for the FOCA files generated locally may be found in this gist. Checking manually e.g. the 'GE32' airspace seems to yield correct result.