相似度分析函数ST_lcsDistance_云数据库 RDS(RDS)-阿里云帮助中心

计算基于LCSS（Longest Common Sub Sequence）算法的两条轨迹的距离。

语法

float8 ST_lcsDisatance(trajectory traj1, trajectory traj2, float8 dist, distanceUnit unit default 'M');
float8 ST_lcsDisatance(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 1- （LCSS）/ min(leafcount(traj1), leafcount(traj2))。

上图中轨迹点1，3，6符合要求，LCSS的数量为3，结果为1-3/5=0.4。

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_LCSDistance(a, b, 100) from traj;
  st_lcsdistance    
-------------------
 0.666666666666667
 (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_LCSDistance(a, b, 100, interval '30 seconds') from traj;
 st_lcsdistance   
-------------------
0.666666666666667 
(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_LCSDistance(a, b, 100, interval '30 seconds', 'M') from traj;
 st_lcsdistance   
-------------------
0.666666666666667 
(1 row)