Polygon with holes (doughnut shape): the EUDR workaround

What the Information System does

It does not accept them: under "Polygons with holes inside", the current specification says such polygons are not accepted and "the user will be shown an error message in this case" (GeoJSON File Description, Common errors 15). The specification's workaround: a doughnut "can be defined by combining two half-doughnut shaped polygons" (GeoJSON File Description, Definitions) (GeoJSON File Description, Common errors 3).

A broken example

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "properties": {
        "ProducerCountry": "CI",
        "ProductionPlace": "Doughnut",
        "Area": 1.1
      },
      "geometry": {
        "type": "Polygon",
        "coordinates": [
          [
            [-5.123456, 6.123456],
            [-5.122456, 6.123456],
            [-5.122456, 6.124456],
            [-5.123456, 6.124456],
            [-5.123456, 6.123456]
          ],
          [
            [-5.123156, 6.123756],
            [-5.122756, 6.123756],
            [-5.122756, 6.124156],
            [-5.123156, 6.124156],
            [-5.123156, 6.123756]
          ]
        ]
      }
    }
  ]
}

What the checker reports for this file:

1. Ring 2 is a hole cut out of the plot. The Information System does not accept polygons with holes and shows an error instead of processing the plot., line 36, column 11

Fix it in EUDRplot

1. Open the file in the checker. Each hole is outlined on the map.
2. Review the cut. Choose Cut the holes out. Each plot with a hole is replaced by pieces without holes that describe the same land; the area before and after is shown for every plot.
3. Accept it. Choose Accept the change and apply. The pieces keep the plot's properties.

Fix it in QGIS

1. Split through the hole. In edit mode, use the Split Features tool and draw a line from outside the plot, across the hole, to outside the plot on the other side. The doughnut becomes two pieces without holes.
2. Check the area. The two pieces together should measure the same as the land around the hole. Check with $area / 10000 in the Field Calculator.
3. Know what Delete holes does. The Delete holes algorithm fills the hole instead, which adds the hole's land to the plot. Use it only if the hole should never have been there.