描述

返回沿给定轨迹插值点的最小距离处点的最小度量。

输入必须是通过 ST_IsValidTrajectory 检查的有效轨迹。如果轨迹在 M 范围内不重叠，则返回 Null。

请参阅 ST_LocateAlong 以获取给定度量处的实际点。

可用性：2.2.0

此函数支持 3d，不会删除 z 索引。

示例

-- Return the time in which two objects moving between 10:00 and 11:00
-- are closest to each other and their distance at that point
WITH inp AS ( SELECT
  ST_AddMeasure('LINESTRING Z (0 0 0, 10 0 5)'::geometry,
    extract(epoch from '2015-05-26 10:00'::timestamptz),
    extract(epoch from '2015-05-26 11:00'::timestamptz)
  ) a,
  ST_AddMeasure('LINESTRING Z (0 2 10, 12 1 2)'::geometry,
    extract(epoch from '2015-05-26 10:00'::timestamptz),
    extract(epoch from '2015-05-26 11:00'::timestamptz)
  ) b
), cpa AS (
  SELECT ST_ClosestPointOfApproach(a,b) m FROM inp
), points AS (
  SELECT ST_Force3DZ(ST_GeometryN(ST_LocateAlong(a,m),1)) pa,
         ST_Force3DZ(ST_GeometryN(ST_LocateAlong(b,m),1)) pb
  FROM inp, cpa
)
SELECT to_timestamp(m) t,
       ST_Distance(pa,pb) distance
FROM points, cpa;

               t               |     distance
-------------------------------+------------------
 2015-05-26 10:45:31.034483+02 | 1.96036833151395

另请参阅

ST_IsValidTrajectory、ST_DistanceCPA、ST_LocateAlong、ST_AddMeasure