名称
ST_LengthSpheroid — 返回椭球体上经度/纬度几何体的 2D 或 3D 长度/周长。
大纲
float ST_LengthSpheroid(geometry a_geometry, spheroid a_spheroid);
描述
Calculates the length or perimeter of a geometry on a spheroid. This is useful if the coordinates of the geometry are in longitude/latitude and a length is desired without reprojection. The spheroid is specified by a text value as follows:
SPHEROID[<NAME>,<SEMI-MAJOR AXIS>,<INVERSE FLATTENING>]
例如：
SPHEROID["GRS_1980",6378137,298.257222101]
可用性：1.2.2
更改：2.2.0 在之前的版本中，这称为 ST_Length_Spheroid 并具有别名 ST_3DLength_Spheroid
该函数支持 3d 并且不会丢失 z-index。
示例
Measure a table geometry directly on a spheroid when the coordinates are stored in longitude and latitude.
SELECT ST_LengthSpheroid(
geometry_column,
'SPHEROID["GRS_1980",6378137,298.257222101]'
)
FROM geometry_table;
This example measures a 2D MultiLineString and each component separately on the same spheroid.
WITH sample AS (
SELECT 'MULTILINESTRING((-118.584 38.374,-118.583 38.5),
(-71.05957 42.3589,-71.061 43))'::geometry AS geom,
CAST('SPHEROID["GRS_1980",6378137,298.257222101]' AS spheroid) AS sph_m
)
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 sample;
tot_len | len_line1 | len_line2 ------------------+------------------+------------------ 85204.52077117894 | 13986.87252824332 | 71217.64824293563
This example uses 3D input; Z contributes to the measured result.
WITH sample AS (
SELECT 'MULTILINESTRING((-118.584 38.374 20,-118.583 38.5 30),
(-71.05957 42.3589 75,-71.061 43 90))'::geometry AS geom,
CAST('SPHEROID["GRS_1980",6378137,298.257222101]' AS spheroid) AS sph_m
)
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 sample;
tot_len | len_line1 | len_line2 ------------------+-----------------+------------------ 85204.52592562366 | 13986.876103023424 | 71217.64982260024