ArcMap

ST_Centroid

定义

ST_Centroid 以面、多面或多线串要素为输入，然后返回位于几何的包络矩形中心的点。这意味着，质心点在几何的最小和最大 x 和 y 范围的中间位置。

语法

Oracle 和 PostgreSQL

sde.st_centroid (polygon sde.st_geometry)
sde.st_centroid (multipolygon sde.st_geometry)
sde.st_centroid (multilinestring sde.st_geometry)

SQLite

st_centroid (polygon geometryblob)
st_centroid (multipolygon geometryblob)
st_centroid (multilinestring geometryblob)

返回类型

ST_Point

示例

城市 GIS 技术人员想要在建筑物密度图中将建筑物覆盖区多面显示为单个点。建筑物覆盖区存储在 bfp 表中，该表由各数据库显示使用的语句所创建并填充。

Oracle

--Create and populate table
CREATE TABLE bfp (
 building_id integer,
 footprint sde.st_geometry);
INSERT INTO bfp VALUES (
 1,
 sde.st_polygon ('polygon ((0 0, 0 10, 10 10, 10 0, 0 0))', 4326)
);
INSERT INTO bfp VALUES (
 2,
 sde.st_polygon ('polygon ((20 0, 30 20, 40 0, 20 0))', 4326)
);
INSERT INTO bfp VALUES (
 3,
 sde.st_polygon ('polygon ((20 30, 25 35, 30 30, 20 30))', 4326)
);

--The ST_Centroid function returns the centroid of each building footprint multipolygon. 
--The ST_AsText function converts each centroid point into a text representation recognized by the application.
SELECT building_id,
 sde.st_astext (sde.st_centroid (footprint)) Centroid
 FROM bfp;
BUILDING_ID                   Centroid
   1                     POINT  (5.00000000 5.00000000)
   2                     POINT  (30.00000000 10.00000000)
   3                     POINT  (25.00000000 32.50000000)

PostgreSQL

--Create and populate table
CREATE TABLE bfp (
 building_id serial,
 footprint sde.st_geometry);
INSERT INTO bfp (footprint) VALUES (
 sde.st_polygon ('polygon ((0 0, 0 10, 10 10, 10 0, 0 0))', 4326)
);
INSERT INTO bfp (footprint) VALUES (
 sde.st_polygon ('polygon ((20 0, 30 20, 40 0, 20 0))', 4326)
);
INSERT INTO bfp (footprint) VALUES (
 sde.st_polygon ('polygon ((20 30, 25 35, 30 30, 20 30))', 4326)
);

--The ST_Centroid function returns the centroid of each building footprint multipolygon. 
--The ST_AsText function converts each centroid point into a text representation recognized by the application.
SELECT building_id, sde.st_astext (sde.st_centroid (footprint)) 
 AS centroid
 FROM bfp;
building_id                  centroid
   1                     POINT  (5 5)
   2                     POINT  (30 10)
   3                     POINT  (25 33)

SQLite

--Create table, add geometry column, and populate table
CREATE TABLE bfp (
 building_id integer primary key autoincrement not null
);
SELECT AddGeometryColumn (
 NULL,
 'bfp',
 'footprint',
 4326,
 'polygon',
 'xy',
 'null'
);
INSERT INTO bfp (footprint) VALUES (
 st_polygon ('polygon ((0 0, 0 10, 10 10, 10 0, 0 0))', 4326)
);
INSERT INTO bfp (footprint) VALUES (
 st_polygon ('polygon ((20 0, 30 20, 40 0, 20 0))', 4326)
);
INSERT INTO bfp (footprint) VALUES (
 st_polygon ('polygon ((20 30, 25 35, 30 30, 20 30))', 4326)
);

--The ST_Centroid function returns the centroid of each building footprint multipolygon. 
--The ST_AsText function converts each centroid point into a text representation recognized by the application.
SELECT building_id, st_astext (st_centroid (footprint)) 
 AS "centroid"
 FROM bfp;
building_id              centroid
   1                     POINT  (5.00000000 5.00000000)
   2                     POINT  (30.00000000 10.0000000)
   3                     POINT  (25.00000000 32.5000000)

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