ST_lcsSimilarity - 云原生数据库 PolarDB

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（m）。
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。仅允许空间参考为 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)