ST_ClosestPointOfApproach — Returns a measure at the closest point of approach of two trajectories.
float8 ST_ClosestPointOfApproach(
geometry track1, geometry track2)
;
Returns the smallest measure at which points interpolated along the given trajectories are the least distance apart.
Inputs must be valid trajectories as checked by ST_IsValidTrajectory. Null is returned if the trajectories do not overlap in their M ranges.
To obtain the actual points at the computed measure use ST_LocateAlong .
Availability: 2.2.0
This function supports 3d and will not drop the z-index.
-- 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_GeometryN(ST_LocateAlong(a,m),1) pa, ST_GeometryN(ST_LocateAlong(b,m),1) pb FROM inp, cpa ) SELECT to_timestamp(m) t, ST_Distance(pa,pb) distance, ST_AsText(pa, 2) AS pa, ST_AsText(pb, 2) AS pb FROM points, cpa; t | distance | pa | pb -------------------------------+--------------------+--------------------------------------+---------------------------------------- 2015-05-26 10:45:31.034483-07 | 1.9603683315139542 | POINT ZM (7.59 0 3.79 1432662331.03) | POINT ZM (9.1 1.24 3.93 1432662331.03)