描述

如果几何在给定距离内，则返回True

为 几何体 ：距离以几何图形的空间参考系定义的单位指定。要使此函数有意义，源几何图形必须位于相同的坐标系中(具有相同的SRID)。

为 地理学 ：单位以米为单位，距离测量默认为 use_spheroid =真。用于更快的评估使用 use_spheroid =False以在球体上测量。

	使用 ST_3DDWithin 用于3D几何图形。

	此函数调用包括一个边界框比较，它利用几何图形上可用的任何索引。

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

可用性：引入了1.5.0地理位置支持

增强：2.1.0提高了地理位置的速度。看见 让地理操作更快捷 有关详细信息，请参阅。

增强：2.1.0引入了对曲线几何图形的支持。

在1.3之前， ST_Expand 通常与以下词结合使用 & & 和ST_Distance来测试距离，在1.3.4之前的版本中，此函数使用该逻辑。从1.3.4开始，ST_DWiThin使用更快的短路距离函数。

示例

-- Find the nearest hospital to each school
-- that is within 3000 units of the school.
--  We do an ST_DWithin search to utilize indexes to limit our search list
--  that the non-indexable ST_Distance needs to process
-- If the units of the spatial reference is meters then units would be meters
SELECT DISTINCT ON (s.gid) s.gid, s.school_name, s.geom, h.hospital_name
  FROM schools s
    LEFT JOIN hospitals h ON ST_DWithin(s.geom, h.geom, 3000)
  ORDER BY s.gid, ST_Distance(s.geom, h.geom);

-- The schools with no close hospitals
-- Find all schools with no hospital within 3000 units
-- away from the school.  Units is in units of spatial ref (e.g. meters, feet, degrees)
SELECT s.gid, s.school_name
  FROM schools s
    LEFT JOIN hospitals h ON ST_DWithin(s.geom, h.geom, 3000)
  WHERE h.gid IS NULL;

-- Find broadcasting towers that receiver with limited range can receive.
-- Data is geometry in Spherical Mercator (SRID=3857), ranges are approximate.

-- Create geometry index that will check proximity limit of user to tower
CREATE INDEX ON broadcasting_towers using gist (geom);

-- Create geometry index that will check proximity limit of tower to user
CREATE INDEX ON broadcasting_towers using gist (ST_Expand(geom, sending_range));

-- Query towers that 4-kilometer receiver in Minsk Hackerspace can get
-- Note: two conditions, because shorter LEAST(b.sending_range, 4000) will not use index.
SELECT b.tower_id, b.geom
  FROM broadcasting_towers b
  WHERE ST_DWithin(b.geom, 'SRID=3857;POINT(3072163.4 7159374.1)', 4000)
    AND ST_DWithin(b.geom, 'SRID=3857;POINT(3072163.4 7159374.1)', b.sending_range);

        

另请参阅

ST_Distance, ST_3DDWithin