對一條軌跡重採樣。
文法
trajectory ST_Resample(trajectory traj, config);參數
參數名稱 | 描述 |
traj | 被重採樣的軌跡對象。 |
config | 重採樣軌跡的規則。格式 |
目前包含以下可選規則，每次調用此函數時，僅可選擇一個規則：
規則名稱 | 參數類型 | 說明 |
add_point.distance_lesser | 浮點數 | 在每條軌跡線上均勻添加點，使每一段之間的距離均小於參數。 |
add_point.period_lesser | 可以轉化為Interval類型的字串 | 在每條軌跡線上均勻添加點，使每一段的時間長度均小於參數。 |
drop_point.distance_lesser | 浮點數 | 如果相鄰多段軌跡線段上所有的點到起點的長度，均小於此參數給定的空間長度時，將其合并（僅保留起點和終點）。 |
drop_point.period_lesser | 可以轉化為Interval類型的字串 | 當相鄰多段軌跡線段的時間長度之和小於給定的時間長度時，將其合并（僅保留起點和終點）。 |
描述
根據提前設定的規則對軌跡對象重採樣，返回重採樣後的軌跡。
樣本
With traj As
(
select '{"trajectory":{"version":1,"type":"STPOINT","leafcount":5,"start_time":"2000-01-01 00:00:00","end_time":"2000-01-05 00:00:00","spatial":"LINESTRING(1 1,10 10,11 11,13 13,15 15)","timeline":["2000-01-01 00:00:00","2000-01-02 00:00:00","2000-01-03 00:00:00","2000-01-04 00:00:00","2000-01-05 00:00:00"]}}'::trajectory a
)
SELECT ST_Resample(a, '{"add_point.distance_lesser":3}') from traj;
st_resample
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
{"trajectory":{"version":1,"type":"STPOINT","leafcount":9,"start_time":"2000-01-01 00:00:00","end_time":"2000-01-05 00:00:00","spatial":"LINESTRING(1 1,2.8 2.8,4.6 4.6,6.4 6.4,8.2 8.2,10 10,11 11,13 13,15 15)","timeline":["2000-01-01 00:00:00","2000-01-01 04:48:00","2000-01-01 09:36:00","2000-01-01 14:24:00","2000-01-01 19:12:00","2000-01-02 00:00:00","2000-01-03 00:00:00","2000-01-04 00:00:00","2000-01-05 00:00:00"]}}
(1 row)
With traj As
(
select '{"trajectory":{"version":1,"type":"STPOINT","leafcount":5,"start_time":"2000-01-01 00:00:00","end_time":"2000-01-05 00:00:00","spatial":"LINESTRING(1 1,10 10,11 11,13 13,15 15)","timeline":["2000-01-01 00:00:00","2000-01-02 00:00:00","2000-01-03 00:00:00","2000-01-04 00:00:00","2000-01-05 00:00:00"]}}'::trajectory a
)
SELECT ST_Resample(a, '{"add_point.period_lesser":"0.5 day"}') from traj;
st_resample
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
{"trajectory":{"version":1,"type":"STPOINT","leafcount":9,"start_time":"2000-01-01 00:00:00","end_time":"2000-01-05 00:00:00","spatial":"LINESTRING(1 1,5.5 5.5,10 10,10.5 10.5,11 11,12 12,13 13,14 14,15 15)","timeline":["2000-01-01 00:00:00","2000-01-01 12:00:00","2000-01-02 00:00:00","2000-01-02 12:00:00","2000-01-03 00:00:00","2000-01-03 12:00:00","2000-01-04 00:00:00","2000-01-04 12:00:00","2000-01-05 00:00:00"]}}
(1 row)
With traj As
(
select '{"trajectory":{"version":1,"type":"STPOINT","leafcount":5,"start_time":"2000-01-01 00:00:00","end_time":"2000-01-05 00:00:00","spatial":"LINESTRING(1 1,10 10,11 11,13 13,15 15)","timeline":["2000-01-01 00:00:00","2000-01-02 00:00:00","2000-01-03 00:00:00","2000-01-04 00:00:00","2000-01-05 00:00:00"]}}'::trajectory a
)
SELECT ST_Resample(a, '{"drop_point.distance_lesser":3}') from traj;
st_resample
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
{"trajectory":{"version":1,"type":"STPOINT","leafcount":4,"start_time":"2000-01-01 00:00:00","end_time":"2000-01-05 00:00:00","spatial":"LINESTRING(1 1,10 10,13 13,15 15)","timeline":["2000-01-01 00:00:00","2000-01-02 00:00:00","2000-01-04 00:00:00","2000-01-05 00:00:00"]}}
(1 row)