调用ST_CurvatureRadius计算轨迹每个中间点的转动半径

计算轨迹每个中间点的转动半径，返回一个浮点数组。

语法

double precision[] ST_CurvatureRadius(trajectory traj, boolean hasdirection default false);

参数

参数名称

描述

traj

轨迹对象。

hasdirection

是否计算轨迹的转向方向。

如果为true，则向逆时针方向转向时，返回负值。

描述

对轨迹的每个中间点（假设某个轨迹有n个点，则其有n-2个中间点），计算轨迹在此点的转动半径。如果在此点沿直线运动，或停留在原地，则转动半径为无穷。转动半径越小说明转弯越急。

示例

SELECT ST_CurvatureRadius(ST_MakeTrajectory('STPOINT'::leaftype,'LINESTRING(0 0, 0 8, 6 8, 12 8, 12 8)', '2000-01-01', '2000-01-01'::timestamp+ '1 day'::interval* (ST_NPoints('LINESTRING(0 0, 0 8, 6 8, 12 8, 12 8)')-1), '{}'));
  st_curvatureradius   
-----------------------
 {5,Infinity,Infinity}


SELECT ST_CurvatureRadius(ST_MakeTrajectory('STPOINT'::leaftype,'LINESTRING(0 0, 0 8, 6 8, 12 8, 12 8, 6 8, 0 8, 0 0)', '2000-01-01', '2000-01-01'::timestamp+ '1 day'::interval* (ST_NPoints('LINESTRING(0 0, 0 8, 6 8, 12 8, 12 8, 6 8, 0 8, 0 0)')-1), '{}'));
st_curvatureradius 
-----------
 {5,Infinity,Infinity,Infinity,Infinity,5}


SELECT ST_CurvatureRadius(ST_MakeTrajectory('STPOINT'::leaftype,'LINESTRING(0 0, 0 8, 6 8, 12 8, 12 8, 6 8, 0 8, 0 0)', '2000-01-01', '2000-01-01'::timestamp+ '1 day'::interval* (ST_NPoints('LINESTRING(0 0, 0 8, 6 8, 12 8, 12 8, 6 8, 0 8, 0 0)')-1), '{}'), true);
 st_curvatureradius 
-----------
 {5,Infinity,Infinity,Infinity,Infinity,-5}


SELECT ST_CurvatureRadius(ST_MakeTrajectory('STPOINT'::leaftype,'LINESTRING(0 0, 0 8, 6 8, 12 8, 12 8, 6 8, 0 8, 0 0, 0 4, 3 4)', '2000-01-01', '2000-01-01'::timestamp+ '1 day'::interval* (ST_NPoints('LINESTRING(0 0, 0 8, 6 8, 12 8, 12 8, 6 8, 0 8, 0 0, 0 4, 3 4)')-1), '{}'), true);
st_curvatureradius
-----------
 {5,Infinity,Infinity,Infinity,Infinity,-5,0,2.5}