描述

计算椭球体上几何体的长度或周长。如果几何体的坐标是经度/纬度，并且希望在不进行重投影的情况下获得长度，这将非常有用。球面体通过文本值指定，如下所示：

例如

可用性：1.2.2

更改：2.2.0 在早期版本中，此函数名为 ST_Length_Spheroid，并具有别名 ST_3DLength_Spheroid

此函数支持 3D，并且不会删除 z 索引。

示例

SELECT ST_LengthSpheroid( geometry_column,
			  'SPHEROID["GRS_1980",6378137,298.257222101]' )
			  FROM geometry_table;

SELECT ST_LengthSpheroid( geom, sph_m ) As tot_len,
ST_LengthSpheroid(ST_GeometryN(geom,1), sph_m) As len_line1,
ST_LengthSpheroid(ST_GeometryN(geom,2), sph_m) As len_line2
			  FROM (SELECT ST_GeomFromText('MULTILINESTRING((-118.584 38.374,-118.583 38.5),
	(-71.05957 42.3589 , -71.061 43))') As geom,
CAST('SPHEROID["GRS_1980",6378137,298.257222101]' As spheroid) As sph_m)  as foo;
	tot_len      |    len_line1     |    len_line2
------------------+------------------+------------------
 85204.5207562955 | 13986.8725229309 | 71217.6482333646

 --3D
SELECT ST_LengthSpheroid( geom, sph_m ) As tot_len,
ST_LengthSpheroid(ST_GeometryN(geom,1), sph_m) As len_line1,
ST_LengthSpheroid(ST_GeometryN(geom,2), sph_m) As len_line2
			  FROM (SELECT ST_GeomFromEWKT('MULTILINESTRING((-118.584 38.374 20,-118.583 38.5 30),
	(-71.05957 42.3589 75, -71.061 43 90))') As geom,
CAST('SPHEROID["GRS_1980",6378137,298.257222101]' As spheroid) As sph_m)  as foo;

	 tot_len      |    len_line1    |    len_line2
------------------+-----------------+------------------
 85204.5259107402 | 13986.876097711 | 71217.6498130292

另请参阅

ST_GeometryN, ST_Length