Name
ST_ClosestPointOfApproach — 返回两个轨迹的最接近点处的度量值。
Synopsis
float8
ST_ClosestPointOfApproach
(
geometry
track1
, geometry
track2
)
;
描述
返回沿给定轨迹插补的点处于最小距离的最小度量值。
输入必须是由检查的有效轨迹 ST_IsValidTrajectory 。如果轨迹在其M范围内不重叠，则返回NULL。
看见 ST_LocateAlong 用于获得给定度量值的实际点数。
可用性：2.2.0
This function supports 3d and will not drop the z-index.
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