名称
ST_LineCrossingDirection — 返回一个数字，指示两个 LineString 的交叉行为
概要
integer ST_LineCrossingDirection(geometry linestringA, geometry linestringB);
描述
给定两条线串，返回一个介于 -3 和 3 之间的整数，表示它们之间存在的交叉行为类型。0 表示没有交叉。此函数仅支持 LINESTRING。
交叉数字具有以下含义：
-
0：线不交叉
-
-1：线交叉向左
-
1：线交叉向右
-
-2：线多重交叉末端向左
-
2：线多重交叉末端向右
-
-3：线多重交叉末端相同首个向左
-
3：线多重交叉末端相同首个向右
可用性：1.4
示例
示例：线交叉向左和线交叉向右
蓝色：线 A；绿色：线 B
SELECT ST_LineCrossingDirection(lineA, lineB) As A_cross_B,
ST_LineCrossingDirection(lineB, lineA) As B_cross_A
FROM (SELECT
ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As lineA,
ST_GeomFromText('LINESTRING (20 140, 71 74, 161 53)') As lineB
) As foo;
A_cross_B | B_cross_A
-----------+-----------
-1 | 1
示例：线多重交叉末端相同首个向左和线多重交叉末端相同首个向右
蓝色：线 A；绿色：线 B
SELECT ST_LineCrossingDirection(lineA, lineB) As A_cross_B,
ST_LineCrossingDirection(lineB, lineA) As B_cross_A
FROM (SELECT
ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As lineA,
ST_GeomFromText('LINESTRING(171 154,20 140,71 74,161 53)') As lineB
) As foo;
A_cross_B | B_cross_A
-----------+-----------
3 | -3
示例：线多重交叉末端向左和线多重交叉末端向右
蓝色：线 A；绿色：线 B
SELECT ST_LineCrossingDirection(lineA, lineB) As A_cross_B,
ST_LineCrossingDirection(lineB, lineA) As B_cross_A
FROM (SELECT
ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As lineA,
ST_GeomFromText('LINESTRING(5 90, 71 74, 20 140, 171 154)') As lineB
) As foo;
A_cross_B | B_cross_A
-----------+-----------
-2 | 2
示例：查找所有交叉的街道
SELECT s1.gid, s2.gid, ST_LineCrossingDirection(s1.geom, s2.geom)
FROM streets s1 CROSS JOIN streets s2
ON (s1.gid != s2.gid AND s1.geom && s2.geom )
WHERE ST_LineCrossingDirection(s1.geom, s2.geom) > 0;