gestionnaire-de-taches-simple/lib/OSM/GeoJsonConverter.php

<?php

namespace OSM;

class GeoJsonConverter
{
    public static function convertRelationToPolygon(
        Element\Relation $relation,
    ): \GeoJson\Geometry\Polygon {
        $positions = [];

        foreach ($relation->getOrderedOuterWays() as $way) {
            foreach ($way->points as $point) {
                $positions[] = new \GeoJson\Geometry\Point([
                    $point->longitude,
                    $point->latitude,
                ]);
            }
        }

        return new \GeoJson\Geometry\Polygon([$positions]);
    }
}