{
    "type": "FeatureCollection",
    "name": "sample_regions",
    "crs": {
        "type": "name",
        "properties": {
            "name": "urn:ogc:def:crs:OGC:1.3:CRS84"
        }
    },
    "features": [
        {
            "type": "Feature",
            "id": 1,
            "properties": {
                "region_id": 1,
                "name": "华北",
                "area_km2": 1540000
            },
            "geometry": {
                "type": "Polygon",
                "coordinates": [
                    [
                        [
                            110.0,
                            36.0
                        ],
                        [
                            120.0,
                            36.0
                        ],
                        [
                            120.0,
                            42.5
                        ],
                        [
                            110.0,
                            42.5
                        ],
                        [
                            110.0,
                            36.0
                        ]
                    ]
                ]
            }
        },
        {
            "type": "Feature",
            "id": 2,
            "properties": {
                "region_id": 2,
                "name": "华东",
                "area_km2": 790000
            },
            "geometry": {
                "type": "Polygon",
                "coordinates": [
                    [
                        [
                            118.0,
                            29.0
                        ],
                        [
                            122.5,
                            29.0
                        ],
                        [
                            122.5,
                            35.0
                        ],
                        [
                            118.0,
                            35.0
                        ],
                        [
                            118.0,
                            29.0
                        ]
                    ]
                ]
            }
        },
        {
            "type": "Feature",
            "id": 3,
            "properties": {
                "region_id": 3,
                "name": "华南",
                "area_km2": 450000
            },
            "geometry": {
                "type": "Polygon",
                "coordinates": [
                    [
                        [
                            110.0,
                            21.0
                        ],
                        [
                            117.0,
                            21.0
                        ],
                        [
                            117.0,
                            25.0
                        ],
                        [
                            110.0,
                            25.0
                        ],
                        [
                            110.0,
                            21.0
                        ]
                    ]
                ]
            }
        }
    ]
}