Python中如何将重叠Polygon合并为带内环的GeoJSON FeatureCollection？

我有如下GeoJSON格式的FeatureCollection数据，包含三个Polygon要素，其中前两个Polygon存在重叠区域：

data_01 = {
    "type": "FeatureCollection",
    "features": [
        {
            "type": "Feature",
            "geometry": {
                "type": "Polygon",
                "coordinates": [
                    [[2, 2], [2, 22], [22, 22], [22, 2], [2, 2]]
                ]
            },
            "properties": {"z": 1412.5, "la": "ba"}
        },
        {
            "type": "Feature",
            "geometry": {
                "type": "Polygon",
                "coordinates": [
                    [[12, 16], [7, 10], [17, 10], [12, 16]]
                ]
            },
            "properties": {"z": 1412.5, "la": "ba"}
        },
        {
            "type": "Feature",
            "geometry": {
                "type": "Polygon",
                "coordinates": [
                    [[27, 15], [24, 12], [29, 12], [27, 15]]
                ]
            },
            "properties": {"z": 1412.5, "la": "ba"}
        }
    ]
}

需求是将重叠的前两个Polygon合并为一个带内环的Polygon，第三个不重叠的Polygon保持独立，最终得到如下结构的data_final：

data_final = {
    "type": "FeatureCollection",
    "features": [
        {
            "type": "Feature",
            "geometry": {
                "type": "Polygon",
                "coordinates": [
                    [[27, 15], [24, 12], [29, 12], [27, 15]]
                ]
            },
            "properties": {"z": 1412.5, "la": "ba"}
        },
        {
            "type": "Feature",
            "geometry": {
                "type": "Polygon",
                "coordinates": [
                    [[2, 2], [2, 22], [22, 22], [22, 2], [2, 2]],
                    [[12, 16], [7, 10], [17, 10], [12, 16]]
                ]
            },
            "properties": {"z": 1412.5, "la": "ba"}
        }
    ]
}

目前已实现数据读取的代码：

import json

with open("data_01.json", 'r', encoding='utf-8-sig') as fh:
    d = fh.read()
    f = json.loads(d)

j = f['features'][0:]

for i in j:
    poly_coord = i['geometry']['coordinates'][0:]
    poly_coord = poly_coord[0]
    print(poly_coord )

实现逻辑与完整代码 #

要完成这个需求，我们可以借助shapely库处理空间几何运算，具体步骤如下：

• 将GeoJSON中的Polygon转换为shapely几何对象，方便进行包含关系判断
• 针对前两个多边形的包含关系，构建带内环的Polygon
• 保留第三个独立多边形，整理为最终的FeatureCollection

完整代码如下：

import json
from shapely.geometry import shape

# 读取GeoJSON数据
with open("data_01.json", 'r', encoding='utf-8-sig') as fh:
    feature_collection = json.load(fh)

features = feature_collection['features']
final_features = []

# 处理前两个重叠多边形
poly1_shape = shape(features[0]['geometry'])
poly2_shape = shape(features[1]['geometry'])

# 检查第二个多边形是否完全被第一个包含（根据你的数据场景）
if poly1_shape.contains(poly2_shape):
    # 提取外环和内环坐标，构建带洞的Polygon
    outer_coords = list(poly1_shape.exterior.coords)
    inner_coords = list(poly2_shape.exterior.coords)
    
    combined_feature = {
        "type": "Feature",
        "geometry": {
            "type": "Polygon",
            "coordinates": [outer_coords, inner_coords]
        },
        "properties": features[0]['properties']
    }
    final_features.append(combined_feature)

# 添加第三个独立多边形
final_features.append(features[2])

# 构建最终的FeatureCollection
data_final = {
    "type": "FeatureCollection",
    "features": final_features
}

# 保存结果到文件（可选）
with open("data_final.json", 'w', encoding='utf-8') as fh:
    json.dump(data_final, fh, indent=2)

# 打印验证结果
print(json.dumps(data_final, indent=2))

代码说明 #

• 使用shapely.geometry.shape将GeoJSON几何转为shapely对象，便于执行空间判断
• 针对你的数据场景，第二个多边形完全处于第一个内部，直接将其坐标作为内环添加到第一个多边形的坐标列表中，形成带洞的Polygon
• 如果后续遇到部分重叠的场景，可以扩展代码使用shapely.ops.unary_union来合并多边形（比如生成MultiPolygon）
• 最终结果可保存为新的GeoJSON文件，或直接用于后续处理

内容的提问来源于stack exchange，提问作者user20567574