ST_LENGTHSPHEROID

📄字数 946

👁️阅读量 加载中...

功能描述

返回椭球体面上几何图形的周长。

语法格式

DOUBLE ST_LENGTHSPHEROID(GEOMETRY a_geometry, spheroid a_spheroid);

参数说明

• a_3dlinestring：目标 GEOMETRY 对象。
• a_spheroid：椭球体由文本值指定。
  • 格式：SPHEROID[<NAME>,<SEMI-MAJOR AXIS>,<INVERSE FLATTENING>]
  • 例如：SPHEROID["GRS_1980",6378137,298.257222101]

函数返回类型

DOUBLE 类型

使用说明

1. 当几何图形的坐标为经度/纬度并且您希望查找没有投影的长度时，请使用此函数。
2. 该函数支持 3d 并且不会丢失 z-index。

示例

SQL> 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   |
+--------------+--------------+--------------+
| 8.520452e+04 | 1.398687e+04 | 7.121765e+04 |
+--------------+--------------+--------------+

(1 row)

--3D
SQL> 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   |
+--------------+--------------+--------------+
| 8.520453e+04 | 1.398688e+04 | 7.121765e+04 |
+--------------+--------------+--------------+

(1 row)