ST_nearestApproachPoint
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Returns the point on a trajectory that is closest to a specified geometry object within a given time window.
Syntax
Two signatures are available. Use the tsrange form when you have a prebuilt range value; use the t1, t2 form when you have two discrete timestamps.
geometry ST_nearestApproachPoint(trajectory traj, tsrange range, geometry g);
geometry ST_nearestApproachPoint(trajectory traj, timestamp t1, timestamp t2, geometry g);Parameters
| Parameter | Description |
|---|---|
traj | The trajectory object to search. |
range | The time range to search within, expressed as a tsrange value. Used in the tsrange signature only. |
t1 | The start time of the search window. Used in the timestamp signature only. |
t2 | The end time of the search window. Used in the timestamp signature only. |
g | The specified geometry object. The function returns the point on the trajectory that is nearest to this geometry. |
Example
The following query finds the point on each trajectory in traj_table that is closest to the line LINESTRING(0 0, 5 5, 9 9), considering only trajectory positions recorded between 13:00 and 14:00 on January 1, 2010. The result is a geometry point value.
-- Find the nearest approach point to a diagonal line within a one-hour window
SELECT ST_nearestApproachPoint(
traj,
'2010-1-1 13:00:00',
'2010-1-1 14:00:00',
'LINESTRING(0 0, 5 5, 9 9)'::geometry
)
FROM traj_table;
-- Returns: a geometry point per row representing the closest position on that
-- trajectory to the specified line within the time window该文章对您有帮助吗？