Returns the spatial deviation between a processed trajectory and the original trajectory, expressed as a floating-point number in the coordinate units of the input trajectories. A larger value indicates greater spatial error introduced by the processing operation (such as compression).
Syntax
float8 ST_deviation(trajectory traj, trajectory after_oper_traj);Parameters
| Parameter | Description |
|---|---|
traj | The original trajectory object. |
after_oper_traj | The processed trajectory object, such as the result of ST_compress. |
Example
The following query checks how much spatial accuracy is lost when compressing a trajectory with a tolerance of 0.001. The return value is in the coordinate units of the input trajectory.
-- Check spatial deviation after compressing with a tolerance of 0.001
SELECT ST_deviation(traj, ST_compress(traj, 0.001)) FROM traj_test;Result:
st_deviation
---------------------
0.00919177345596219
(1 row)See also
[ST_compress](): Compress a trajectory object using a specified tolerance.
该文章对您有帮助吗？