名称
ST_LineCrossingDirection — 返回一个数字，指示两条 LineString 的交叉行为
概要
integer ST_LineCrossingDirection(geometry linestringA, geometry linestringB);
描述
给定两条线字符串，返回一个介于 -3 到 3 之间的整数，指示它们之间存在何种交叉行为。0 表示没有交叉。这仅适用于 LINESTRING。
交叉数具有以下含义
0: LINE NO CROSS
-1: LINE CROSS LEFT
1: LINE CROSS RIGHT
-2: LINE MULTICROSS END LEFT
2: LINE MULTICROSS END RIGHT
-3: LINE MULTICROSS END SAME FIRST LEFT
3: LINE MULTICROSS END SAME FIRST RIGHT
可用性: 1.4
示例
示例: LINE CROSS LEFT 和 LINE CROSS RIGHT
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: LINE MULTICROSS END SAME FIRST LEFT 和 LINE MULTICROSS END SAME FIRST RIGHT
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: LINE MULTICROSS END LEFT 和 LINE MULTICROSS END RIGHT
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;