ST_BuildArea
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名称

ST_BuildArea — 创建由几何体的线条形成的多边形几何体。

大纲

geometry ST_BuildArea(geometry geom);

描述

创建由输入几何体的组成线条形成的面几何体。 输入可以是 LineString、MultiLineString、Polygon、MultiPolygon 或 GeometryCollection。 结果是多边形或多多边形，具体取决于输入。 如果输入线条未形成多边形，则返回 NULL。

与 ST_MakePolygon 不同，此函数接受由多条线形成的环，并且可以形成任意数量的多边形。

此功能将内环转换为孔。 要将内环也转换为多边形，请使用 ST_Polygonize。

[注意]

输入线条必须正确，节点才能使此功能正常工作。ST_Node可用于节点线。

如果输入线条交叉，此函数将生成无效的多边形。ST_MakeValid可用于确保输出有效。

可用性：1.1.0

示例

Building an area from five input lines.

Code
WITH data(geom) AS (VALUES
   ('LINESTRING (180 40,30 20,20 90)'::geometry),
  ('LINESTRING (180 40,160 160)'::geometry),
  ('LINESTRING (160 160,80 190,80 120,20 90)'::geometry),
  ('LINESTRING (80 60,120 130,150 80)'::geometry),
  ('LINESTRING (80 60,150 80)'::geometry)
)
SELECT ST_BuildArea(ST_Collect(geom )) AS wkt
    FROM data;
栅格输出
POLYGON((180 40,30 20,20 90,80 120,80 190,160 160,180 40),(150 80,120 130,80 60,150 80))
Figure
Geometry figure for visual-st-buildarea-01

Create a donut from two circular polygons.

Code
WITH input AS (
  SELECT 'POINT(100 90)'::geometry AS geom
),
rings AS (
  SELECT ST_Buffer(geom, 25, 'quad_segs=1') AS inring,
         ST_Buffer(geom, 50, 'quad_segs=1') AS outring
  FROM input
)
SELECT inring AS inner_ring,
       outring AS outer_ring,
       ST_BuildArea(ST_Collect(inring, outring)) AS area
FROM rings;
栅格输出
-[ RECORD 1 ]-----
inner_ring | POLYGON((125 90,100 65,75 90,100 115,125 90))
outer_ring | POLYGON((150 90,100 40,50 90,100 140,150 90))
area       | POLYGON((150 90,100 40,50 90,100 140,150 90),(125 90,100 115,75 90,100 65,125 90))
Figure
Geometry figure for visual-st-buildarea-02

Input linework that crosses at non-endpoint intersections must be noded before building areas:

Code
WITH lines(geom) AS (VALUES
  ('LINESTRING(36 35,45 307)'::geometry),
  ('LINESTRING(30 290,390 280)'::geometry),
  ('LINESTRING(320 60,300 310)'::geometry),
  ('LINESTRING(20 60,320 60)'::geometry),
  ('LINESTRING(120 140,168 225)'::geometry),
  ('LINESTRING(140 220,220 150,120 170)'::geometry)
),
noded AS (
  SELECT ST_Node(ST_UnaryUnion(ST_Collect(geom))) AS geom FROM lines
)
SELECT ST_BuildArea(geom) AS area
FROM noded;
栅格输出
POLYGON((320 60,36.8 60,44.4 289.6,302.2 282.4,320 60),(156.9 205.3,135.2 167,220 150,156.9 205.3))
Figure
Geometry figure for visual-st-buildarea-03

相关信息

ST_Collect, ST_MakePolygon, ST_MakeValid, ST_Node, ST_Polygonize, ST_BdPolyFromText, ST_BdMPolyFromText (使用标准 OGC 接口对该函数进行包装)