2つのベクトルの角度算出

ベクトルp1、p2と、ベクトルp3、p4の角度を算出するプログラム

postgresで実行。

SELECT ABS(
    CASE WHEN diff_deg > 180 THEN diff_deg - 360
    ELSE diff_deg END
) AS diff_deg
FROM (
    SELECT ABS(
        DEGREES( ST_Azimuth( p1, p2 )) - DEGREES( ST_Azimuth( p3, p4 ))
    ) AS diff_deg
    FROM (
        SELECT
            ST_GeomFromText('POINT(0 0)') p1,
            ST_GeomFromText('POINT(1 1)') p2,
            ST_GeomFromText('POINT(0 0)') p3,
            ST_GeomFromText('POINT(1 2)') p4
    ) AS p
) AS tmp