计算LCSS轨迹段与traj1在这段轨迹上的距离。
语法
float8 ST_lcsSubDisatance(trajectory traj1, trajectory traj2, float8 dist, distanceUnit unit default 'M');
float8 ST_lcsSubDisatance(trajectory traj1, trajectory traj2, float8 dist, interval lag, distanceUnit unit default 'M');
参数
参数名称 | 描述 |
traj1 | 轨迹对象1。 |
traj2 | 轨迹对象2。 |
dist | 两点之间的距离容差,单位为米(m)。 |
lag | 两点之间的时间容差。 |
unit | 距离单位,允许以下值:
|
描述
本函数计算的是与LCSS轨迹段相对应的轨迹1子轨迹的点数与LCSS轨迹段的点数的比例关系。
上图中轨迹点[2,3,5]为LCSS轨迹段,轨迹1与此对应的轨迹段为[2,3,4,5],返回的结果为1-3/4。
数值越小表明LCSS轨迹与轨迹1的相似度越高。
通常trajectory对象中会有srid值,如果trajectory对象没有srid值,则默认为4326。
示例
With traj AS (
Select ST_makeTrajectory('STPOINT', 'LINESTRINGZ(114.000528 33.588163 54.87 , 114.000535 33.588235 54.85 , 114.000447 33.588272 54.69 , 114.000348 33.588287 54.73 , 114.000245 33.588305 55.26 , 114.000153 33.588305 55.3)'::geometry,
ARRAY['2010-01-01 11:30'::timestamp, '2010-01-01 11:31', '2010-01-01 11:32', '2010-01-01 11:33','2010-01-01 11:34','2010-01-01 11:35'], NULL) a,
ST_makeTrajectory('STPOINT', 'LINESTRINGZ(114.000529 33.588163 54.87 , 114.000535 33.578235 54.85 , 114.000447 33.578272 54.69 , 114.000348 33.578287 54.73 , 114.000245 33.578305 55.26 , 114.000163 33.588305 55.3)'::geometry,
ARRAY['2010-01-01 11:29:58'::timestamp, '2010-01-01 11:31:02', '2010-01-01 11:33', '2010-01-01 11:33:09','2010-01-01 11:34','2010-01-01 11:34:30'], NULL) b)
Select st_LCSSubDistance(a, b, 100) from traj;
st_lcssubdistance
------------------------
0.66666666666666666667
(1 row)
With traj AS (
Select ST_makeTrajectory('STPOINT', 'LINESTRINGZ(114.000528 33.588163 54.87 , 114.000535 33.588235 54.85 , 114.000447 33.588272 54.69 , 114.000348 33.588287 54.73 , 114.000245 33.588305 55.26 , 114.000153 33.588305 55.3)'::geometry,
ARRAY['2010-01-01 11:30'::timestamp, '2010-01-01 11:31', '2010-01-01 11:32', '2010-01-01 11:33','2010-01-01 11:34','2010-01-01 11:35'], NULL) a,
ST_makeTrajectory('STPOINT', 'LINESTRINGZ(114.000529 33.588163 54.87 , 114.000535 33.578235 54.85 , 114.000447 33.578272 54.69 , 114.000348 33.578287 54.73 , 114.000245 33.578305 55.26 , 114.000163 33.588305 55.3)'::geometry,
ARRAY['2010-01-01 11:29:58'::timestamp, '2010-01-01 11:31:02', '2010-01-01 11:33', '2010-01-01 11:33:09','2010-01-01 11:34','2010-01-01 11:34:30'], NULL) b)
Select st_LCSSubDistance(a, b, 100, interval '30 seconds') from traj;
st_lcssubdistance
-------------------
0.666666666666667
(1 row)
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