计算基于LCSS(Longest Common Sub Sequence)算法的两条轨迹的相似度。

语法

integer ST_lcsSimilarity(trajectory traj1, trajectory traj2, float8 dist, distanceUnit unit default 'M' );
integer ST_lcsSimilarity(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。
lag 两点之间的时间容差。
unit 距离单位,允许以下值:
  • 'M' : 米
  • 'KM': 千米
  • 'D': 度,只允许空间参考为 WGS84(4326)轨迹使用

描述

LCSS用于计算最大的公共子序列。用于判断两个轨迹点是否一致的条件包括空间距离和时间距离。 返回的结果是符合条件的轨迹点的数量 。



上图中轨迹点1,3, 6 符合要求,返回为 3。

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_LCSSimilarity(a, b, 100) from traj;
  st_lcssimilarity    
-------------------
 2
 (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 11:34:15','2010-01-01 11:34:50','2010-01-01 11:34:30'], NULL) b)
Select st_LCSSimilarity(a, b, 100, interval '30 seconds') from traj;
 st_lcssimilarity   
-------------------
2 
(1 row)