GeometryCollection in EUDR files: accepted, but check what's inside
A GeometryCollection groups several geometries into one feature. The EU Information System accepts it, but what's inside still has to follow every other rule, and mixed collections are a common source of problems.
What the EU documentation says
The GeoJSON File Description defines GeometryCollection as "two or more geometries" and notes that any geometry type other than GeometryCollection must have a coordinates member (a collection instead has a list of geometries). The DDS API reference lists GeometryCollection among the supported types, alongside Point, MultiPoint, Polygon and MultiPolygon. LineString and MultiLineString are not accepted anywhere, including inside a collection.
Where GeometryCollections come from
- KML Placemarks with several geometries (a MultiGeometry, for example a plot boundary plus a centre point). The Plot File Checker, for one, reads such a Placemark as a GeometryCollection.
- GIS "merge" or "collect" operations on mixed layers.
- Tools that store a polygon and its label point together.
The problems to look for
- A line inside: the collection contains a LineString, which isn't valid for a production place. That's an error.
- Points mixed with polygons: a plot described by both its boundary and a point. Which one is the plot? A point inside a polygon of the same plot adds nothing, and a point with no Area is treated as 4 ha.
- Invalid members: each polygon in the collection must itself be closed, without holes and without self-intersections.
The cleaner alternative
If every member is the same kind, use the matching multi-type instead:
- several polygons for one producer's plot or plots: MultiPolygon;
- several points: MultiPoint.
Or give each plot its own Feature in the FeatureCollection, with its own properties. Separate features are easier to check, and each can carry its own ProductionPlace name and Area.
What the Plot File Checker does
- A collection of only polygons, or only points: info. The checker merges it into a MultiPolygon or MultiPoint in the fixed file.
- A collection mixing points and polygons: a warning, left for you to decide which geometry describes the plot.
- A collection containing a line: an error.
- Member polygons are checked exactly like any polygon: closure, decimals, holes, self-intersection.
Before you upload
Open the file on a map and click a few collection features. If you see a boundary with a dot in the middle, or a path along a road, clean the feature so that only the plot geometry remains. Then save and check the file again: removing a member can leave a collection with a single geometry, which is simpler to write as that geometry on its own.